Tuesday, March 25, 2014

Oracle Interview Questions - New interview questions for Oracle Specialists

General Questions

  • Tell us about yourself/ your background.
  • What are the three major characteristics that you bring to the job market?
  • What motivates you to do a good job?
  • What two or three things are most important to you at work?
  • What qualities do you think are essential to be successful in this kind of work?
  • What courses did you attend? What job certifications do you hold?
  • What subjects/courses did you excel in? Why?
  • What subjects/courses gave you trouble? Why?
  • How does your previous work experience prepare you for this position?
  • How do you define 'success'?
  • What has been your most significant accomplishment to date?
  • Describe a challenge you encountered and how you dealt with it.
  • Describe a failure and how you dealt with it.
  • Describe the 'ideal' job... the 'ideal' supervisor.
  • What leadership roles have you held?
  • What prejudices do you hold?
  • What do you like to do in your spare time?
  • What are your career goals (a) 3 years from now; (b) 10 years from now?
  • How does this position match your career goals?
  • What have you done in the past year to improve yourself?
  • In what areas do you feel you need further education and training to be successful?
  • What do you know about our company?
  • Why do you want to work for this company. Why should we hire you?
  • Where do you see yourself fitting in to this organization ...initially? ...in 5 years?
  • Why are you looking for a new job?
  • How do you feel about re-locating?
  • Are you willing to travel?
  • What are your salary requirements?
  • When would you be available to start if you were selected?

Here are few interview questions with answers found on the internet. As I don't have time to format these questions to wiki I am just posting them hoping someone to format them.

Oracle Interview Questions

1. Explain the difference between a hot backup and a cold backup and the benefits associated with each.
A hot backup is basically taking a backup of the database while it is still up and running and it must be in archive log mode. A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode. The benefit of taking a hot backup is that the database is still available for use while the backup is occurring and you can recover the database to any point in time. The benefit of taking a cold backup is that it is typically easier to administer the backup and recovery process. In addition, since you are taking cold backups the database does not require being in archive log mode and thus there will be a slight performance gain as the database is not cutting archive logs to disk.
2. You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?
I would create a text based backup control file, stipulating where on disk all the data files were and then issue the recover command with the using backup control file clause.
3. How do you switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.
4. Explain the difference between a data block, an extent and a segment.
A data block is the smallest unit of logical storage for a database object. As objects grow they take chunks of additional storage that are composed of contiguous data blocks. These groupings of contiguous data blocks are called extents. All the extents that an object takes when grouped together are considered the segment of the database object.
5. Give two examples of how you might determine the structure of the table DEPT.
Use the describe command or use the dbms_metadata.get_ddl package.
6. Where would you look for errors from the database engine?
In the alert log.
7. Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces few rollback data. The delete command, on the other hand, is a DML operation, which will produce rollback data and thus take longer to complete.
8. Give the reasoning behind using an index.
Faster access to data blocks in a table.
9. Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact table contains measurements while dimension tables will contain data that will help describe the fact tables.
10. What type of index should you use on a fact table?
A Bitmap index.
11. Give some examples of the types of database contraints you may find in Oracle and indicate their purpose.
  • A Primary or Unique Key can be used to enforce uniqueness on one or more columns.
  • A Referential Integrity Contraint can be used to enforce a Foreign Key relationship between two tables.
  • A Not Null constraint - to ensure a value is entered in a column
  • A Value Constraint - to check a column value against a specific set of values.
12. A table is classified as a parent table and you want to drop and re-create it. How would you do this without affecting the children tables?
Disable the foreign key constraint to the parent, drop the table, re-create the table, enable the foreign key constraint.
13. Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to each.
ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all transactions that have occurred in the database so that you can recover to any point in time. NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the disadvantage of not being able to recover to any point in time. NOARCHIVELOG mode does have the advantage of not having to write transactions to an archive log and thus increases the performance of the database slightly.
14. What command would you use to create a backup control file?
Alter database backup control file to trace.
15. Give the stages of instance startup to a usable state where normal users may access it.
STARTUP NOMOUNT - Instance startup
STARTUP MOUNT - The database is mounted
STARTUP OPEN - The database is opened
16. What column differentiates the V$ views to the GV$ views and how?
The INST_ID column which indicates the instance in a RAC environment the information came from.
17. How would you go about generating an EXPLAIN plan?
Create a plan table with utlxplan.sql.
Use the explain plan set statement_id = 'tst1' into plan_table for a SQL statement
Look at the explain plan with utlxplp.sql or utlxpls.sql
18. How would you go about increasing the buffer cache hit ratio?
Use the buffer cache advisory over a given workload and then query the v$db_cache_advice table. If a change was necessary then I would use the alter system set db_cache_size command.
19. Explain an ORA-01555.
You get this error when you get a snapshot too old within rollback. It can usually be solved by increasing the undo retention or increasing the size of rollbacks. You should also look at the logic involved in the application getting the error message.
20. Explain the difference between $ORACLE_HOME and $ORACLE_BASE.
ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.

Oracle Interview Questions

1. How would you determine the time zone under which a database was operating?
SELECT dbtimezone FROM DUAL;
2. Explain the use of setting GLOBAL_NAMES equal to TRUE.
It ensure the use of consistent naming conventions for databases and links in a networked environment.
3. What command would you use to encrypt a PL/SQL application?
4. Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.
They are all named PL/SQL blocks.
Function must return a value. Can be called inside a query.
Procedure may or may not return value.
Package is the collection of functions, procedures, variables which can be logically grouped together.
5. Explain the use of table functions.
6. Name three advisory statistics you can collect.
7. Where in the Oracle directory tree structure are audit traces placed?
8. Explain materialized views and how they are used.
9. When a user process fails, what background process cleans up after it?
10. What background process refreshes materialized views?
Job Queue Process (CJQ)
11. How would you determine what sessions are connected and what resources they are waiting for?
12. Describe what redo logs are.
13. How would you force a log switch?
alter system switch logfile;
14. Give two methods you could use to determine what DDL changes have been made.
15. What does coalescing a tablespace do?
Coalesce simply takes contigous free extents and makes them into a single bigger free extent.
16. What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?
TEMP tablespace gets cleared once the transaction is done where as PERMANENT tablespace retails the data.
17. Name a tablespace automatically created when you create a database.
18. When creating a user, what permissions must you grant to allow them to connect to the database?
Grant create session to username;
19. How do you add a data file to a tablespace?
alter tablespace USERS add datafile '/ora01/oradata/users02.dbf' size 50M;
20. How do you resize a data file?
alter database datafile '/ora01/oradata/users02.dbf' resize 100M;
21. What view would you use to look at the size of a data file?
22. What view would you use to determine free space in a tablespace?
23. How would you determine who has added a row to a table?
By implementing an INSERT trigger for logging details during each INSERT operation on the table
24. How can you rebuild an index?
25. Explain what partitioning is and what its benefit is.
A table partition is also a table segment, and by using partitioning technique we can enhance performance of table access.
26. You have just compiled a PL/SQL package but got errors, how would you view the errors?
show errors
27. How can you gather statistics on a table?
exec dbms_stats.gather_table_stats
Also, remember to analyze all associated indexes on that table using dbms_stats.gather_index_stats
28. How can you enable a trace for a session?
alter session set sql_trace='TRUE';
29. What is the difference between the SQL*Loader and IMPORT utilities?
SQL*LOADER loads external data which is in OS files to oracle database tables while IMPORT utility imports data only which is exported by EXPORT utility of oracle database.
30. Name two files used for network connection to a database.

Oracle Interview Questions

1. Describe the difference between a procedure, function and anonymous pl/sql block. Candidate should mention use of DECLARE statement, a function must return a value while a procedure doesn't have to.

2. What is a mutating table error and how can you get around it? This happens with triggers. It occurs because the trigger is trying to update a row it is currently using. The usual fix involves either use of views or temporary tables so the database is selecting from one while updating the other.

3. Describe the use of %ROWTYPE and %TYPE in PL/SQL Expected answer: %ROWTYPE allows you to associate a variable with an entire table row. The %TYPE associates a variable with a single column type.

4. What packages (if any) has Oracle provided for use by developers? Expected answer: Oracle provides the DBMS_ series of packages. There are many which developers should be aware of such as DBMS_SQL, DBMS_PIPE, DBMS_TRANSACTION, DBMS_LOCK, DBMS_ALERT, DBMS_OUTPUT, DBMS_JOB, DBMS_UTILITY, DBMS_DDL, UTL_FILE. If they can mention a few of these and describe how they used them, even better. If they include the SQL routines provided by Oracle, great, but not really what was asked.

5. Describe the use of PL/SQL tables Expected answer: PL/SQL tables are scalar arrays that can be referenced by a binary integer. They can be used to hold values for use in later queries or calculations. In Oracle 8 they will be able to be of the %ROWTYPE designation, or RECORD.

6. When is a declare statement needed ? The DECLARE statement is used in PL/SQL anonymous blocks such as with stand alone, non-stored PL/SQL procedures. It must come first in a PL/SQL stand alone file if it is used.

7. In what order should a open/fetch/loop set of commands in a PL/SQL block be implemented if you use the %NOTFOUND cursor variable in the exit when statement? Why? Expected answer: OPEN then FETCH then LOOP followed by the exit when. If not specified in this order will result in the final return being done twice because of the way the %NOTFOUND is handled by PL/SQL.

8. What are SQLCODE and SQLERRM and why are they important for PL/SQL developers? Expected answer: SQLCODE returns the value of the error number for the last error encountered. The SQLERRM returns the actual error message for the last error encountered. They can be used in exception handling to report, or, store in an error log table, the error that occurred in the code. These are especially useful for the WHEN OTHERS exception.

9. How can you find within a PL/SQL block, if a cursor is open? Expected answer: Use the %ISOPEN cursor status variable.

10. How can you generate debugging output from PL/SQL? Expected answer: Use the DBMS_OUTPUT package. Another possible method is to just use the SHOW ERROR command, but this only shows errors. The DBMS_OUTPUT package can be used to show intermediate results from loops and the status of variables as the procedure is executed. The new package UTL_FILE can also be used.

11. What are the types of triggers? Expected Answer: There are 12 types of triggers in PL/SQL that consist of combinations of the BEFORE, AFTER, ROW, TABLE, INSERT, UPDATE, DELETE and ALL key words: BEFORE ALL ROW INSERT AFTER ALL ROW INSERT BEFORE INSERT AFTER INSERT etc.

Oracle Interview Questions

1. A tablespace has a table with 30 extents in it. Is this bad? Why or why not.
Multiple extents in and of themselves aren?t bad. However if you also have chained rows this can hurt performance.

2. How do you set up tablespaces during an Oracle installation?
You should always attempt to use the Oracle Flexible Architecture standard or another partitioning scheme to ensure proper separation of SYSTEM, ROLLBACK, REDO LOG, DATA, TEMPORARY and INDEX segments.

3. You see multiple fragments in the SYSTEM tablespace, what should you check first?
Ensure that users don?t have the SYSTEM tablespace as their TEMPORARY or DEFAULT tablespace assignment by checking the DBA_USERS view.

4. What are some indications that you need to increase the SHARED_POOL_SIZE parameter?
Poor data dictionary or library cache hit ratios, getting error ORA-04031. Another indication is steadily decreasing performance with all other tuning parameters the same.

5. What is the general guideline for sizing db_block_size and db_multi_block_read for an application that does many full table scans?
Oracle almost always reads in 64k chunks. The two should have a product equal to 64 or a multiple of 64.

6. What is the fastest query method for a table
Fetch by rowid

7. Explain the use of TKPROF? What initialization parameter should be turned on to get full TKPROF output?
The tkprof tool is a tuning tool used to determine cpu and execution times for SQL statements. You use it by first setting timed_statistics to true in the initialization file and then turning on tracing for either the entire database via the sql_trace parameter or for the session using the ALTER SESSION command. Once the trace file is generated you run the tkprof tool against the trace file and then look at the output from the tkprof tool. This can also be used to generate explain plan output.

8. When looking at v$sysstat you see that sorts (disk) is high. Is this bad or good? If bad -How do you correct it?
If you get excessive disk sorts this is bad. This indicates you need to tune the sort area parameters in the initialization files. The major sort are parameter is the SORT_AREA_SIZe parameter.

9. When should you increase copy latches? What parameters control copy latches
When you get excessive contention for the copy latches as shown by the "redo copy" latch hit ratio. You can increase copy latches via the initialization parameter LOG_SIMULTANEOUS_COPIES to twice the number of CPUs on your system.

10. Where can you get a list of all initialization parameters for your instance? How about an indication if they are default settings or have been changed
You can look in the init.ora file for an indication of manually set parameters. For all parameters, their value and whether or not the current value is the default value, look in the v$parameter view.

11. Describe hit ratio as it pertains to the database buffers. What is the difference between instantaneous and cumulative hit ratio and which should be used for tuning
The hit ratio is a measure of how many times the database was able to read a value from the buffers verses how many times it had to re-read a data value from the disks. A value greater than 80-90% is good, less could indicate problems. If you simply take the ratio of existing parameters this will be a cumulative value since the database started. If you do a comparison between pairs of readings based on some arbitrary time span, this is the instantaneous ratio for that time span. Generally speaking an instantaneous reading gives more valuable data since it will tell you what your instance is doing for the time it was generated over.

12. Discuss row chaining, how does it happen? How can you reduce it? How do you correct it
Row chaining occurs when a VARCHAR2 value is updated and the length of the new value is longer than the old value and won?t fit in the remaining block space. This results in the row chaining to another block. It can be reduced by setting the storage parameters on the table to appropriate values. It can be corrected by export and import of the effected table.

Oracle Interview Questions

1. Give one method for transferring a table from one schema to another:
There are several possible methods, export-import, CREATE TABLE... AS SELECT, or COPY.

2. What is the purpose of the IMPORT option IGNORE? What is it?s default setting
The IMPORT IGNORE option tells import to ignore "already exists" errors. If it is not specified the tables that already exist will be skipped. If it is specified, the error is ignored and the tables data will be inserted. The default value is N.

3. You have a rollback segment in a version 7.2 database that has expanded beyond optimal, how can it be restored to optimal
Use the ALTER TABLESPACE ..... SHRINK command.

4. If the DEFAULT and TEMPORARY tablespace clauses are left out of a CREATE USER command what happens? Is this bad or good? Why
The user is assigned the SYSTEM tablespace as a default and temporary tablespace. This is bad because it causes user objects and temporary segments to be placed into the SYSTEM tablespace resulting in fragmentation and improper table placement (only data dictionary objects and the system rollback segment should be in SYSTEM).

5. What are some of the Oracle provided packages that DBAs should be aware of
Oracle provides a number of packages in the form of the DBMS_ packages owned by the SYS user. The packages used by DBAs may include: DBMS_SHARED_POOL, DBMS_UTILITY, DBMS_SQL, DBMS_DDL, DBMS_SESSION, DBMS_OUTPUT and DBMS_SNAPSHOT. They may also try to answer with the UTL*.SQL or CAT*.SQL series of SQL procedures. These can be viewed as extra credit but aren?t part of the answer.

6. What happens if the constraint name is left out of a constraint clause
The Oracle system will use the default name of SYS_Cxxxx where xxxx is a system generated number. This is bad since it makes tracking which table the constraint belongs to or what the constraint does harder.

7. What happens if a tablespace clause is left off of a primary key constraint clause
This results in the index that is automatically generated being placed in then users default tablespace. Since this will usually be the same tablespace as the table is being created in, this can cause serious performance problems.

8. What is the proper method for disabling and re-enabling a primary key constraint
You use the ALTER TABLE command for both. However, for the enable clause you must specify the USING INDEX and TABLESPACE clause for primary keys.

9. What happens if a primary key constraint is disabled and then enabled without fully specifying the index clause
The index is created in the user?s default tablespace and all sizing information is lost. Oracle doesn?t store this information as a part of the constraint definition, but only as part of the index definition, when the constraint was disabled the index was dropped and the information is gone.

10. (On UNIX) When should more than one DB writer process be used? How many should be used
If the UNIX system being used is capable of asynchronous IO then only one is required, if the system is not capable of asynchronous IO then up to twice the number of disks used by Oracle number of DB writers should be specified by use of the db_writers initialization parameter.

11. You are using hot backup without being in archivelog mode, can you recover in the event of a failure? Why or why not
You can?t use hot backup without being in archivelog mode. So no, you couldn?t recover.

12. What causes the "snapshot too old" error? How can this be prevented or mitigated
This is caused by large or long running transactions that have either wrapped onto their own rollback space or have had another transaction write on part of their rollback space. This can be prevented or mitigated by breaking the transaction into a set of smaller transactions or increasing the size of the rollback segments and their extents.

13. How can you tell if a database object is invalid By checking the status column of the DBA_, ALL_ or USER_OBJECTS views, depending upon whether you own or only have permission on the view or are using a DBA account.

13. A user is getting an ORA-00942 error yet you know you have granted them permission on the table, what else should you check
You need to check that the user has specified the full name of the object (select empid from scott.emp; instead of select empid from emp;) or has a synonym that balls to the object (create synonym emp for scott.emp;)

14. A developer is trying to create a view and the database won?t let him. He has the "DEVELOPER" role which has the "CREATE VIEW" system privilege and SELECT grants on the tables he is using, what is the problem
You need to verify the developer has direct grants on all tables used in the view. You can?t create a stored object with grants given through views.

15. If you have an example table, what is the best way to get sizing data for the production table implementation
The best way is to analyze the table and then use the data provided in the DBA_TABLES view to get the average row length and other pertinent data for the calculation. The quick and dirty way is to look at the number of blocks the table is actually using and ratio the number of rows in the table to its number of blocks against the number of expected rows.

16. How can you find out how many users are currently logged into the database? How can you find their operating system id
There are several ways. One is to look at the v$session or v$process views. Another way is to check the current_logins parameter in the v$sysstat view. Another if you are on UNIX is to do a "ps -ef|grep oracle|wc -l? command, but this only works against a single instance installation.

17. A user selects from a sequence and gets back two values, his select is: SELECT pk_seq.nextval FROM dual;What is the problem Somehow two values have been inserted into the dual table. This table is a single row, single column table that should only have one value in it.

18. How can you determine if an index needs to be dropped and rebuilt
Run the ANALYZE INDEX command on the index to validate its structure and then calculate the ratio of LF_BLK_LEN/LF_BLK_LEN+BR_BLK_LEN and if it isn?t near 1.0 (i.e. greater than 0.7 or so) then the index should be rebuilt. Or if the ratio BR_BLK_LEN/ LF_BLK_LEN+BR_BLK_LEN is nearing 0.3.

Oracle Interview Questions

1. How can variables be passed to a SQL routine
By use of the & symbol. For passing in variables the numbers 1-8 can be used (&1, &2,...,&8) to pass the values after the command into the SQLPLUS session. To be prompted for a specific variable, place the ampersanded variable in the code itself: "select * from dba_tables where owner=&owner_name;" . Use of double ampersands tells SQLPLUS to resubstitute the value for each subsequent use of the variable, a single ampersand will cause a reprompt for the value unless an ACCEPT statement is used to get the value from the user.

2. You want to include a carriage return/linefeed in your output from a SQL script, how can you do this
The best method is to use the CHR() function (CHR(10) is a return/linefeed) and the concatenation function "||". Another method, although it is hard to document and isn?t always portable is to use the return/linefeed as a part of a quoted string.

3. How can you call a PL/SQL procedure from SQL
By use of the EXECUTE (short form EXEC) command.

4. How do you execute a host operating system command from within SQL
By use of the exclamation ball "!" (in UNIX and some other OS) or the HOST (HO) command.

5. You want to use SQL to build SQL, what is this called and give an example
This is called dynamic SQL. An example would be: set lines 90 pages 0 termout off feedback off verify off spool drop_all.sql select ?drop user ?||username||? cascade;? from dba_users where username not in ("SYS?,?SYSTEM?); spool off Essentially you are looking to see that they know to include a command (in this case DROP USER...CASCADE;) and that you need to concatenate using the ?||? the values selected from the database.

6. What SQLPlus command is used to format output from a select
This is best done with the COLUMN command.

7. You want to group the following set of select returns, what can you group on
Max(sum_of_cost), min(sum_of_cost), count(item_no), item_no The only column that can be grouped on is the "item_no" column, the rest have aggregate functions associated with them.

8. What special Oracle feature allows you to specify how the cost based system treats a SQL statement
The COST based system allows the use of HINTs to control the optimizer path selection. If they can give some example hints such as FIRST ROWS, ALL ROWS, USING INDEX, STAR, even better.

9. You want to determine the location of identical rows in a table before attempting to place a unique index on the table, how can this be done
Oracle tables always have one guaranteed unique column, the rowid column. If you use a min/max function against your rowid and then select against the proposed primary key you can squeeze out the rowids of the duplicate rows pretty quick. For example: select rowid from emp e where e.rowid > (select min(x.rowid) from emp x where x.emp_no = e.emp_no); In the situation where multiple columns make up the proposed key, they must all be used in the where clause.

10. What is a Cartesian product
A Cartesian product is the result of an unrestricted join of two or more tables. The result set of a three table Cartesian product will have x * y * z number of rows where x, y, z correspond to the number of rows in each table involved in the join.

11. You are joining a local and a remote table, the network manager complains about the traffic involved, how can you reduce the network traffic Push the processing of the remote data to the remote instance by using a view to pre-select the information for the join. This will result in only the data required for the join being sent across.

11. What is the default ordering of an ORDER BY clause in a SELECT statement

12. What is tkprof and how is it used
The tkprof tool is a tuning tool used to determine cpu and execution times for SQL statements. You use it by first setting timed_statistics to true in the initialization file and then turning on tracing for either the entire database via the sql_trace parameter or for the session using the ALTER SESSION command. Once the trace file is generated you run the tkprof tool against the trace file and then look at the output from the tkprof tool. This can also be used to generate explain plan output.

13. What is explain plan and how is it used
The EXPLAIN PLAN command is a tool to tune SQL statements. To use it you must have an explain_table generated in the user you are running the explain plan for. This is created using the utlxplan.sql script. Once the explain plan table exists you run the explain plan command giving as its argument the SQL statement to be explained. The explain_plan table is then queried to see the execution plan of the statement. Explain plans can also be run using tkprof.

14. How do you set the number of lines on a page of output? The width
The SET command in SQLPLUS is used to control the number of lines generated per page and the width of those lines, for example SET PAGESIZE 60 LINESIZE 80 will generate reports that are 60 lines long with a line width of 80 characters. The PAGESIZE and LINESIZE options can be shortened to PAGES and LINES.

15. How do you prevent output from coming to the screen
The SET option TERMOUT controls output to the screen. Setting TERMOUT OFF turns off screen output. This option can be shortened to TERM.

16. How do you prevent Oracle from giving you informational messages during and after a SQL statement execution
The SET options FEEDBACK and VERIFY can be set to OFF.

17. How do you generate file output from SQL
By use of the SPOOL comm

Oracle Interview Questions

A CO-RELATED SUBQUERY is one that has a correlation name as table or view designator in the FROM clause of the outer query and the same correlation name as a qualifier of a search condition in the WHERE clause of the subquery. eg
    SELECT  field1 from table1 X
    WHERE  field2>(select avg(field2) from table1 Y

(The subquery in a correlated subquery is revaluated for every row of the table or view named in the outer query.)

2. What are various joins used while writing SUBQUERIES
Self join-Its a join foreign key of a table references the same table.
Outer Join--Its a join condition used where One can query all the rows of one of the tables in the join condition even though they don't satisfy the join condition.
Equi-join--Its a join condition that retrieves rows from one or more tables in which one or more columns in one table are equal to one or more columns in the second table.

3. What are various constraints used in SQL

4. What are different Oracle database objects

5. What is difference between Rename and Alias
Rename is a permanent name given to a table or column whereas Alias is a temporary name given to a table or column which do not exist once the SQL statement is executed.

6. What is a view
A view is stored procedure based on one or more tables, its a virtual table.

7. What are various privileges that a user can grant to another user

8. What is difference between UNIQUE and PRIMARY KEY constraints
A table can have only one PRIMARY KEY whereas there can be any number of UNIQUE keys. The columns that compose PK are automatically define NOT NULL, whereas a column that compose a UNIQUE is not automatically defined to be mandatory must also specify the column is NOT NULL.

9. Can a primary key contain more than one columns

10. How you will avoid duplicating records in a query

11. What is difference between SQL and SQL*PLUS
SQL*PLUS is a command line tool where as SQL and PL/SQL language interface and reporting tool. Its a command line tool that allows user to type SQL commands to be executed directly against an Oracle database. SQL is a language used to query the relational database(DML,DCL,DDL). SQL*PLUS commands are used to format query result, Set options, Edit SQL commands and PL/SQL.

12. Which datatype is used for storing graphics and images
LONG RAW data type is used for storing BLOB's (binary large objects).

13. How will you delete duplicating rows from a base table
DELETE FROM table_name A WHERE rowid>(SELECT min(rowid) from table_name B where B.table_no=A.table_no);
DROP old_table RENAME new_table TO old_table DELETE FROM table_name A WHERE rowid NOT IN (SELECT MAX(ROWID) FROM table_name GROUP BY column_name)

14. What is difference between SUBSTR and INSTR
SUBSTR returns a specified portion of a string eg SUBSTR('BCDEF',4) output BCDE INSTR provides character position in which a pattern is found in a string.
eg INSTR('ABC-DC-F','-',2) output 7 (2nd occurence of '-')
15. There is a string '120000 12 0 .125' ,how you will find the position of the decimal place
INSTR('120000 12 0 .125','.',1) output 13 
16. There is a '%' sign in one field of a column. What will be the query to find it.
'\' Should be used before '%'.
17. When you use WHERE clause and when you use HAVING clause
HAVING clause is used when you want to specify a condition for a group function and it is written after GROUP BY clause The WHERE clause is used when you want to specify a condition for columns, single row functions except group functions and it is written before GROUP BY clause if it is used.
18. Which is more faster - IN or EXISTS
EXISTS is more faster than IN because EXISTS returns a Boolean value whereas IN returns a value.
Appropriate answer will be....
Result of the subquery is small Then "IN" is typicaly more appropriate. and Result of the subquery is big/large/long Then "EXIST" is more appropriate.
19. What is a OUTER JOIN
Outer Join--Its a join condition used where you can query all the rows of one of the tables in the join condition even though they dont satisfy the join condition.
20. How you will avoid your query from using indexes
SELECT * FROM emp Where emp_no+' '=12345;
i.e you have to concatenate the column name with space within codes in the where condition.
SELECT /*+ FULL(a) */ ename, emp_no from emp where emp_no=1234;
i.e using HINTS

Oracle Interview Questions

1. What is a pseudo column. Give some examples
It is a column that is not an actual column in the table.
Suppose customer table is there having different columns like customer no, payments.What will be the query to select top three max payments.
For top N queries, see http://www.orafaq.com/forum/mv/msg/160920/472554/102589/#msg_472554 post

2. What is the purpose of a cluster.
Oracle does not allow a user to specifically locate tables, since that is a part of the function of the RDBMS. However, for the purpose of increasing performance, oracle allows a developer to create a CLUSTER. A CLUSTER provides a means for storing data from different tables together for faster retrieval than if the table placement were left to the RDBMS.

3. What is a cursor.
Oracle uses work area to execute SQL statements and store processing information PL/SQL construct called a cursor lets you name a work area and access its stored information A cursor is a mechanism used to fetch more than one row in a Pl/SQl block.

4. Difference between an implicit & an explicit cursor.
PL/SQL declares a cursor implicitly for all SQL data manipulation statements, including quries that return only one row. However,queries that return more than one row you must declare an explicit cursor or use a cursor FOR loop.
Explicit cursor is a cursor in which the cursor name is explicitly assigned to a SELECT statement via the CURSOR...IS statement. An implicit cursor is used for all SQL statements Declare, Open, Fetch, Close. An explicit cursors are used to process multirow SELECT statements An implicit cursor is used to process INSERT, UPDATE, DELETE and single row SELECT. .INTO statements.

5. What are cursor attributes

6. What is a cursor for loop.
Cursor For Loop is a loop where oracle implicitly declares a loop variable, the loop index that of the same record type as the cursor's record.

7. Difference between NO DATA FOUND and %NOTFOUND
NO DATA FOUND is an exception raised only for the SELECT....INTO statements when the where clause of the querydoes not match any rows. When the where clause of the explicit cursor does not match any rows the %NOTFOUND attribute is set to TRUE instead.

8. What a SELECT FOR UPDATE cursor represent.
SELECT......FROM......FOR......UPDATE[OF column-reference][NOWAIT] The processing done in a fetch loop modifies the rows that have been retrieved by the cursor. A convenient way of modifying the rows is done by a method with two parts: the FOR UPDATE clause in the cursor declaration, WHERE CURRENT OF CLAUSE in an UPDATE or declaration statement.

9. What 'WHERE CURRENT OF ' clause does in a cursor.
                         SELECT  num_credits  INTO  v_numcredits  FROM classes
                         WHERE  dept=123 and course=101;
                         UPDATE  students
                         SET current_credits=current_credits+v_numcredits
                         WHERE  CURRENT OF  X;
                         END  LOOP

10. What is use of a cursor variable? How it is defined.
A cursor variable is associated with different statements at run time, which can hold different values at run time. Static cursors can only be associated with one run time query. A cursor variable is reference type(like a pointer in C). Declaring a cursor variable: TYPE type_name IS REF CURSOR RETURN return_type type_name is the name of the reference type,return_type is a record type indicating the types of the select list that will eventually be returned by the cursor variable.

11. What should be the return type for a cursor variable.Can we use a scalar data type as return type.
The return type for a cursor must be a record type.It can be declared explicitly as a user-defined or %ROWTYPE can be used. eg TYPE t_studentsref IS REF CURSOR RETURN students%ROWTYPE

12. How you open and close a cursor variable.Why it is required.
OPEN cursor variable FOR SELECT...Statement CLOSE cursor variable In order to associate a cursor variable with a particular SELECT statement OPEN syntax is used.In order to free the resources used for the query CLOSE statement is used.

13. How you were passing cursor variables in PL/SQL 2.2.
In PL/SQL 2.2 cursor variables cannot be declared in a package.This is because the storage for a cursor variable has to be allocated using Pro*C or OCI with version 2.2,the only means of passing a cursor variable to a PL/SQL block is via bind variable or a procedure parameter.

14. Can cursor variables be stored in PL/SQL tables.If yes how.If not why.
No, a cursor variable points a row which cannot be stored in a two-dimensional PL/SQL table.

15. Difference between procedure and function.
Functions are named PL/SQL blocks that return a value and can be called with arguments procedure a named block that can be called with parameter. A procedure all is a PL/SQL statement by itself, while a Function call is called as part of an expression.

16. What are different modes of parameters used in functions and procedures.

17. What is difference between a formal and an actual parameter
The variables declared in the procedure and which are passed, as arguments are called actual, the parameters in the procedure declaration. Actual parameters contain the values that are passed to a procedure and receive results. Formal parameters are the placeholders for the values of actual parameters

18. Can the default values be assigned to actual parameters.

19. Can a function take OUT parameters.If not why.
Yes. A function return a value, but can also have one or more OUT parameters. it is best practice, however to use a procedure rather than a function if you have multiple values to return.

20. What is syntax for dropping a procedure and a function .Are these operations possible.

              Drop Procedure procedure_name
              Drop Function function_name

Using ORACLE PRECOMPILERS ,SQL statements and PL/SQL blocks can be contained inside 3GL programs written in C,C++,COBOL,PASCAL, FORTRAN,PL/1 AND ADA. The Precompilers are known as Pro*C,Pro*Cobol,... This form of PL/SQL is known as embedded pl/sql,the language in which pl/sql is embedded is known as the host language. The prcompiler translates the embedded SQL and pl/sql ststements into calls to the precompiler runtime library.The output must be compiled and linked with this library to creater an executable.

22. What is OCI. What are its uses.
Oracle Call Interface is a method of accesing database from a 3GL program. Uses--No precompiler is required,PL/SQL blocks are executed like other DML statements.
                     The OCI library provides
                    -functions to parse SQL statemets
                    -bind input variables
                    -bind output variables
                    -execute statements
                    -fetch the results

23. Difference between database triggers and form triggers.
a) Data base trigger(DBT) fires when a DML operation is performed on a data base table.Form trigger(FT) Fires when user presses a key or navigates between fields on the screen b) Can be row level or statement level No distinction between row level and statement level. c) Can manipulate data stored in Oracle tables via SQL Can manipulate data in Oracle tables as well as variables in forms. d) Can be fired from any session executing the triggering DML statements. Can be fired only from the form that define the trigger. e) Can cause other database triggers to fire.Can cause other database triggers to fire,but not other form triggers.

24. What is an UTL_FILE.What are different procedures and functions associated
with it. UTL_FILE is a package that adds the ability to read and write to operating system files Procedures associated with it are FCLOSE, FCLOSE_ALL and 5 procedures to output data to a file PUT, PUT_LINE, NEW_LINE, PUTF, FFLUSH.PUT, FFLUSH.PUT_LINE,FFLUSH.NEW_LINE. Functions associated with it are FOPEN, ISOPEN.

25. Can you use a commit statement within a database trigger.

26. What is the maximum buffer size that can be specified using the DBMS_OUTPUT.ENABLE function?

Oracle Interview Questions

1. When looking at the estat events report you see that you are getting busy buffer waits. Is this bad? How can you find what is causing it
Buffer busy waits could indicate contention in redo, rollback or data blocks. You need to check the v$waitstat view to see what areas are causing the problem. The value of the "count" column tells where the problem is, the "class" column tells you with what. UNDO is rollback segments, DATA is data base buffers.

2. If you see contention for library caches how can you fix it
Increase the size of the shared pool.

3. If you see statistics that deal with "undo" what are they really talking about
Rollback segments and associated structures.

4. If a tablespace has a default pctincrease of zero what will this cause (in relationship to the smon process)
The SMON process won?t automatically coalesce its free space fragments.

5. If a tablespace shows excessive fragmentation what are some methods to defragment the tablespace? (7.1,7.2 and 7.3 only)
In Oracle 7.0 to 7.2 The use of the 'alter session set events 'immediate trace name coalesce level ts#';? command is the easiest way to defragment contiguous free space fragmentation. The ts# parameter corresponds to the ts# value found in the ts$ SYS table. In version 7.3 the ?alter tablespace coalesce;? is best. If the free space isn?t contiguous then export, drop and import of the tablespace contents may be the only way to reclaim non-contiguous free space.

6. How can you tell if a tablespace has excessive fragmentation
If a select against the dba_free_space table shows that the count of a tablespaces extents is greater than the count of its data files, then it is fragmented.

7. You see the following on a status report: redo log space requests 23 redo log space wait time 0 Is this something to worry about? What if redo log space wait time is high? How can you fix this Since the wait time is zero, no. If the wait time was high it might indicate a need for more or larger redo logs.

8. What can cause a high value for recursive calls? How can this be fixed
A high value for recursive calls is cause by improper cursor usage, excessive dynamic space management actions, and or excessive statement re-parses. You need to determine the cause and correct it By either relinking applications to hold cursors, use proper space management techniques (proper storage and sizing) or ensure repeat queries are placed in packages for proper reuse.

9. If you see a pin hit ratio of less than 0.8 in the estat library cache report is this a problem? If so, how do you fix it
This indicate that the shared pool may be too small. Increase the shared pool size.

10. If you see the value for reloads is high in the estat library cache report is this a matter for concern
Yes, you should strive for zero reloads if possible. If you see excessive reloads then increase the size of the shared pool.

11. You look at the dba_rollback_segs view and see that there is a large number of shrinks and they are of relatively small size, is this a problem? How can it be fixed if it is a problem
A large number of small shrinks indicates a need to increase the size of the rollback segment extents. Ideally you should have no shrinks or a small number of large shrinks. To fix this just increase the size of the extents and adjust optimal accordingly.

12. You look at the dba_rollback_segs view and see that you have a large number of wraps is this a problem
A large number of wraps indicates that your extent size for your rollback segments are probably too small. Increase the size of your extents to reduce the number of wraps. You can look at the average transaction size in the same view to get the information on transaction size.

Oracle Interview Questions

1. You have just started a new instance with a large SGA on a busy existing server. Performance is terrible, what should you check for
The first thing to check with a large SGA is that it isn?t being swapped out.

2. What OS user should be used for the first part of an Oracle installation (on UNIX)
You must use root first.

3. When should the default values for Oracle initialization parameters be used as is

4. How many control files should you have? Where should they be located
At least 2 on separate disk spindles. Be sure they say on separate disks, not just file systems.

5. How many redo logs should you have and how should they be configured for maximum recoverability
You should have at least three groups of two redo logs with the two logs each on a separate disk spindle (mirrored by Oracle). The redo logs should not be on raw devices on UNIX if it can be avoided.

6. You have a simple application with no "hot" tables (i.e. uniform IO and access requirements). How many disks should you have assuming standard layout for SYSTEM, USER, TEMP and ROLLBACK tablespaces
At least 7, see disk configuration answer above.

7. Describe third normal form
Something like: In third normal form all attributes in an entity are related to the primary key and only to the primary key

8. Is the following statement true or false:
"All relational databases must be in third normal form" False. While 3NF is good for logical design most databases, if they have more than just a few tables, will not perform well using full 3NF. Usually some entities will be denormalized in the logical to physical transfer process.

9. What is an ERD
An ERD is an Entity-Relationship-Diagram. It is used to show the entities and relationships for a database logical model.

10. Why are recursive relationships bad? How do you resolve them
A recursive relationship (one where a table relates to itself) is bad when it is a hard relationship (i.e. neither side is a "may" both are "must") as this can result in it not being possible to put in a top or perhaps a bottom of the table (for example in the EMPLOYEE table you couldn?t put in the PRESIDENT of the company because he has no boss, or the junior janitor because he has no subordinates). These type of relationships are usually resolved by adding a small intersection entity.

11. What does a hard one-to-one relationship mean (one where the relationship on both ends is "must")
Expected answer: This means the two entities should probably be made into one entity.

12. How should a many-to-many relationship be handled
By adding an intersection entity table

13. What is an artificial (derived) primary key? When should an artificial (or derived) primary key be used
A derived key comes from a sequence. Usually it is used when a concatenated key becomes too cumbersome to use as a foreign key.

Oracle Interview Questions

1. When should you consider denormalization
Whenever performance analysis indicates it would be beneficial to do so without compromising data integrity.

2. How can you determine if an Oracle instance is up from the operating system level
There are several base Oracle processes that will be running on multi-user operating systems, these will be smon, pmon, dbwr and lgwr. Any answer that has them using their operating system process showing feature to check for these is acceptable. For example, on UNIX a ps -ef|grep dbwr will show what instances are up.

3. Users from the PC clients are getting messages indicating : ORA-06114: (Cnct err, can't get err txt. See Servr Msgs & Codes Manual)

What could the problem be The instance name is probably incorrect in their connection string.

4. Users from the PC clients are getting the following error stack: ERROR: ORA-01034: ORACLE not available ORA-07318: smsget: open error when opening sgadef.dbf file. HP-UX Error: 2: No such file or directory

What is the probable cause The Oracle instance is shutdown that they are trying to access, restart the instance.

5. How can you determine if the SQLNET process is running for SQLNET V1? How about V2
For SQLNET V1 check for the existence of the orasrv process. You can use the command "tcpctl status" to get a full status of the V1 TCPIP server, other protocols have similar command formats. For SQLNET V2 check for the presence of the LISTENER process(s) or you can issue the command "lsnrctl status".

6. What file will give you Oracle instance status information? Where is it located
The alert.ora log. It is located in the directory specified by the background_dump_dest parameter in the v$parameter table.

7. Users aren?t being allowed on the system. The following message is received: ORA-00257 archiver is stuck. Connect internal only, until freed What is the problem The archive destination is probably full, backup the archive logs and remove them and the archiver will re-start.

8. Where would you look to find out if a redo log was corrupted assuming you are using Oracle mirrored redo logs
There is no message that comes to the SQLDBA or SRVMGR programs during startup in this situation, you must check the alert.log file for this information.

9. You attempt to add a datafile and get: ORA-01118: cannot add anymore datafiles: limit of 40 exceeded What is the problem and how can you fix it When the database was created the db_files parameter in the initialization file was set to 40. You can shutdown and reset this to a higher value, up to the value of MAX_DATAFILES as specified at database creation. If the MAX_DATAFILES is set to low, you will have to rebuild the control file to increase it before proceeding.

10. You look at your fragmentation report and see that smon hasn?t coalesced any of you tablespaces, even though you know several have large chunks of contiguous free extents. What is the problem

Check the dba_tablespaces view for the value of pct_increase for the tablespaces. If pct_increase is zero, smon will not coalesce their free space.

11. Your users get the following error: ORA-00055 maximum number of DML locks exceeded What is the problem and how do you fix it The number of DML Locks is set by the initialization parameter DML_LOCKS. If this value is set to low (which it is by default) you will get this error. Increase the value of DML_LOCKS. If you are sure that this is just a temporary problem, you can have them wait and then try again later and the error should clear.

12. You get a call from you backup DBA while you are on vacation. He has corrupted all of the control files while playing with the ALTER DATABASE BACKUP CONTROLFILE command. What do you do
As long as all datafiles are safe and he was successful with the BACKUP controlfile command you can do the following: CONNECT INTERNAL STARTUP MOUNT (Take any read-only tablespaces offline before next step ALTER DATABASE DATAFILE .... OFFLINE;) RECOVER DATABASE USING BACKUP CONTROLFILE ALTER DATABASE OPEN RESETLOGS; (bring read-only tablespaces back online) Shutdown and backup the system, then restart If they have a recent output file from the ALTER DATABASE BACKUP CONTROL FILE TO TRACE; command, they can use that to recover as well. If no backup of the control file is available then the following will be required: CONNECT INTERNAL STARTUP NOMOUNT CREATE CONTROL FILE .....; However, they will need to know all of the datafiles, logfiles, and settings for MAXLOGFILES, MAXLOGMEMBERS, MAXLOGHISTORY, MAXDATAFILES for the database to use the command.

Oracle Interview Questions

1. How would you determine the time zone under which a database was operating? 2. Explain the use of setting GLOBAL_NAMES equal to TRUE. 3. What command would you use to encrypt a PL/SQL application? 4. Explain the difference between a FUNCTION, PROCEDURE and PACKAGE. 5. Explain the use of table functions. 6. Name three advisory statistics you can collect. 7. Where in the Oracle directory tree structure are audit traces placed? 8. Explain materialized views and how they are used. 9. When a user process fails, what background process cleans up after it? 10. What background process refreshes materialized views? 11. How would you determine what sessions are connected and what resources they are waiting for? 12. Describe what redo logs are. 13. How would you force a log switch? 14. Give two methods you could use to determine what DDL changes have been made. 15. What does coalescing a tablespace do? 16. What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace? 17. Name a tablespace automatically created when you create a database. 18. When creating a user, what permissions must you grant to allow them to connect to the database? 19. How do you add a data file to a tablespace? 20. How do you resize a data file? 21. What view would you use to look at the size of a data file? 22. What view would you use to determine free space in a tablespace? 23. How would you determine who has added a row to a table? 24. How can you rebuild an index? 25. Explain what partitioning is and what its benefit is. 26. You have just compiled a PL/SQL package but got errors, how would you view the errors? 27. How can you gather statistics on a table? 28. How can you enable a trace for a session? 29. What is the difference between the SQL*Loader and IMPORT utilities? 30. Name two files used for network connection to a database.

Oracle Interview Questions

1. In a system with an average of 40 concurrent users you get the following from a query on rollback extents:

-------------------------- R01 11
R02 8
R03 12
R04 9

You have room for each to grow by 20 more extents each. Is there a problem? Should you take any action
No there is not a problem. You have 40 extents showing and an average of 40 concurrent users. Since there is plenty of room to grow no action is needed.

2. You see multiple extents in the temporary tablespace. Is this a problem
As long as they are all the same size this isn?t a problem. In fact, it can even improve performance since Oracle won?t have to create a new extent when a user needs one.

3. Define OFA.
OFA stands for Optimal Flexible Architecture. It is a method of placing directories and files in an Oracle system so that you get the maximum flexibility for future tuning and file placement.

4. How do you set up your tablespace on installation
The answer here should show an understanding of separation of redo and rollback, data and indexes and isolation os SYSTEM tables from other tables. An example would be to specify that at least 7 disks should be used for an Oracle installation so that you can place
  • SYSTEM tablespace on one
  • Redo logs on two (mirrored redo logs)
  • TEMPORARY tablespace on another,
  • ROLLBACK tablespace on another and
  • still have two for DATA and INDEXES.
They should indicate how they will handle archive logs and exports as well. As long as they have a logical plan for combining or further separation more or less disks can be specified.

5. What should be done prior to installing Oracle (for the OS and the disks)
adjust kernel parameters or OS tuning parameters in accordance with installation guide. Be sure enough contiguous disk space is available.

6. You have installed Oracle and you are now setting up the actual instance. You have been waiting an hour for the initialization script to finish, what should you check first to determine if there is a problem
Check to make sure that the archiver isn?t stuck. If archive logging is turned on during install a large number of logs will be created. This can fill up your archive log destination causing Oracle to stop to wait for more space.

7. When configuring SQLNET on the server what files must be set up

8. When configuring SQLNET on the client what files need to be set up

9. What must be installed with ODBC on the client in order for it to work with Oracle
SQLNET and PROTOCOL (for example: TCPIP adapter) layers of the transport programs.

General Oracle Questions

  • What Oracle products have you worked with?
  • What version of Oracle were you running?
  • Compare Oracle to any other database that you know. Why would you prefer to work on one and not on the other?

Oracle DBA Questions

Typical DBA questions: 1. How many databases and what sizes?
2. Did you use online or off-line backups? Why?

used both based on business needs.
3. If you have to advise a backup strategy for a new application, how would you approach it and what questions will you ask?

is down time allowed, and what is this being used for Prod,QA or Dev. how huge this Db gonna be in few months .. what type of data is being used in this DB etc..
4. If a customer calls you about a hanging database session, what will you do to resolve it?

first thing ...any errors , if not check for session status.. locks waits , disk io, explain plan .. etc
5. How many control files and redo logs should a database have? atleast

2 ctl's and 3 logs

Oracle Developer Questions

Typical Developer questions:
  • Tell us about the projects you've worked on.
  • What language was the application written in?
  • What programming languages are you familiar with?
  • What technologies did you use?


1. What does a COMMIT statement do to a CURSOR

a] Open the Cursor
b] Fetch the Cursor
c] Close the Cursor
d] None of the above
Ans : D
2. Which of the following is TRUE

1] Host variables are declared anywhere in the program
2] Host variables are declared in the DECLARE section
a] Only 1 is TRUE
b] Only 2 is TRUE
c] Both 1 & 2are TRUE
d] Both are FALSE
Ans : B
3. Which of the following is NOT VALID is PL/SQL

a] Bool boolean;
b] NUM1, NUM2 number;
c] deptname dept.dname%type;
d] date1 date := sysdate
Ans : B
4. Declare
fvar number := null; svar number := 5
goto << fproc>>
if fvar is null then
<< fproc>>
svar := svar + 5
end if;
What will be the value of svar after the execution ?
a] Error
b] 10
c] 5
d] None of the above
Ans : A

5. Which of the following is not correct about an Exception ?

a] Raised automatically / Explicitly in response to an ORACLE_ERROR
b] An exception will be raised when an error occurs in that block
c] Process terminates after completion of error sequence.
d] A Procedure or Sequence of statements may be processed.
Ans : C
6. Which of the following is not correct about User_Defined Exceptions ?

a] Must be declared
b] Must be raised explicitly
c] Raised automatically in response to an Oracle error
d] None of the above
Ans : C
7. A Stored Procedure is a

a] Sequence of SQL or PL/SQL statements to perform specific function
b] Stored in compiled form in the database
c] Can be called from all client environments
d] All of the above
Ans : D
8. Which of the following statement is false

a] Any procedure can raise an error and return an user message and error number
b] Error number ranging from 20000 to 20999 are reserved for user defined messages
c] Oracle checks Uniqueness of User defined errors
d] Raise_Application_error is used for raising an user defined error.
Ans : C
9. Is it possible to open a cursor which is in a Package in another procedure ?

a] Yes
b] No
Ans : A
10. Is it possible to use Transactional control statements in Database Triggers ?

a] Yes
b] No
Ans : B
11. Is it possible to Enable or Disable a Database trigger ?

a] Yes
b] No
Ans : A
12. PL/SQL supports datatype(s)

a] Scalar datatype
b] Composite datatype
c] All of the above
d] None of the above
Ans C
13. Find the ODD data type out

d] RAW
Ans : B
14. Which of the following is not correct about the "TABLE" data type ?

a] Can contain any no of columns
b] Simulates a One-dimensional array of unlimited size
c] Column datatype of any Scalar type
d] None of the above
Ans : A
15. Find the ODD one out of the following

Ans C
16. Which of the following is not correct about Cursor ?

a] Cursor is a named Private SQL area
b] Cursor holds temporary results
c] Cursor is used for retrieving multiple rows
d] SQL uses implicit Cursors to retrieve rows
Ans : B
18. Which of the following is NOT VALID in PL/SQL ?

a] Select ... into
b] Update
c] Create
d] Delete
Ans : C
19. What is the Result of the following 'VIK'||NULL||'RAM' ?

a] Error
Ans : C
20. Declare
a number := 5; b number := null; c number := 10;
if a > b AND a < c then
a := c * a;
end if;
What will be the value of 'a' after execution ?
a] 50
c] 5
d] None of the above
Ans : C

21. Does the Database trigger will fire when the table is TRUNCATED ?

a] Yes
b] No
Ans : B

Ans : C
23. REPLACE('JACK AND JUE','J','BL') will return

d] None of the above
Ans : C
24. TRANSLATE('333SQD234','0123456789ABCDPQRST','0123456789') will return

a] 333234
b] 333333
c] 234333
d] None of the above
Ans : A
A812 NARAYAN 5000
A973 UMESH 2850
A500 BALAJI 5750
Use these data for the following Questions
Select SAL from EMP E1 where 3 > ( Select count(*) from Emp E2
where E1.SAL > E2.SAL ) will retrieve
a] 3500,5000,2500
b] 5000,2850
c] 2850,5750
d] 5000,5750
Ans : A
26. Is it possible to modify a Data type of a column when column contains data ?

a] Yes
b] No
Ans B
27. Which of the following is not correct about a View ?

a] To protect some of the columns of a table from other users
b] Occupies data storage space
c] To hide complexity of a query
d] To hide complexity of a calculations
Ans : B
28. Which is not part of the Data Definition Language ?

  Ans : C
29. The Data Manipulation Language statements are

d] All of the above
Ans : D
A812 NARAYAN 5000
A500 BALAJI 5750
Using the above data Select count(sal) from Emp will retrieve
a] 1
b] 0
c] 3
d] None of the above
Ans : C
31. If an UNIQUE KEY constraint on DATE column is created, will it accept the rows that are inserted with SYSDATE ?

a] Will
b] Won't
Ans : B
32. What are the different events in Triggers ?

a] Define, Create
b] Drop, Comment
c] Insert, Update, Delete
d] All of the above
Ans : C

33. What built-in subprogram is used to manipulate images in image items ?

a] Zoom_out
b] Zoom_in'
c] Image_zoom
d] Zoom_image
Ans : C
34. Can we pass RECORD GROUP between FORMS ?

a] Yes
b] No
Ans : A
36. SHOW_ALERT function returns

a] Boolean
b] Number
c] Character
d] None of the above
Ans : B
37. What SYSTEM VARIABLE is used to refer DATABASE TIME ?

a] $$dbtime$$
b] $$time$$
c] $$datetime$$
d] None of the above
Ans : A
38. :SYSTEM.EFFECTIVE.DATE variable is

a] Read only
b] Read & Write
c] Write only
d] None of the above
Ans : C
39.. How can you CALL Reports from Forms4.0 ?

a] Run_Report built_in
b] Call_Report built_in
c] Run_Product built_in
d] Call_Product built_in
Ans : C
85. When do you get a .PLL extension ?
a] Save Library file
b] Generate Library file
c] Run Library file
d] None of the above
Ans : A
40. What is built_in Subprogram ?

a] Stored procedure & Function
b] Collection of Subprogram
c] Collection of Packages
d] None of the above
Ans : D
41. GET_BLOCK property is a

a] Restricted procedure
b] Unrestricted procedure
c] Library function
d] None of the above

Sunday, March 9, 2014

Oracle Forms Reports Questions and Answers - Oracle Forms Interviews

What is the Maximum allowed length of Record group Column?
Record group column names cannot exceed 30 characters.

Which parameter can be used to set read level consistency across multiple queries?
Read only

What are the different types of Record Groups?
Query Record Groups
NonQuery Record Groups
State Record Groups

From which designation is it preferred to send the output to the printed?

What are difference between post database commit and post-form commit?
Post-form commit fires once during the post and commit transactions process, after the database commit occurs. The post-form-commit trigger fires after inserts, updates and deletes have been posted to the database but before the transactions have been finalized in the issuing the command. The post-database-commit trigger fires after oracle forms issues the commit to finalized transactions.

What are the different display styles of list items?
Pop_listText_listCombo box

Which of the above methods is the faster method?
performing the calculation in the query is faster.

With which function of summary item is the compute at options required?
percentage of total functions.

What are parameters?
Parameters provide a simple mechanism for defining and setting the valuesof inputs that are required by a form at startup. Form parameters are variables of type char,number,date that you define at design time.

What are the three types of user exits available ?
Oracle Precompiler exits, Oracle call interface, NonOracle user exits.

How many windows in a form can have console?
Only one window in a form can display the console, and you cannot change the console assignment at runtime.

What is an administrative (privileged) user? (for DBA )
Oracle DBAs and operators typically use administrative accounts to manage the database and database instance. An administrative account is a user that is granted SYSOPER or SYSDBA privileges. SYSDBA and SYSOPER allow access to a database instance even if it is not running. Control of these privileges is managed outside of the database via password files and special operating system groups. This password file is created with the orapwd utility.

What are the two repeating frame always associated with matrix object?
One down repeating frame below one across repeating frame.

What are the master-detail triggers?

How does one connect to an administrative user? (for DBA )
If an administrative user belongs to the "dba" group on Unix, or the "ORA_DBA" (ORA_sid_DBA) group on NT, he/she can connect like this:
connect / as sysdba
No password is required. This is equivalent to the desupported "connect internal" method.
A password is required for "non-secure" administrative access. These passwords are stored in password files. Remote connections via Net8 are classified as non-secure. Look at this example:
connect sys/password as sysdba

How does one create a password file? (for DBA )
The Oracle Password File ($ORACLE_HOME/dbs/orapw or orapwSID) stores passwords for users with administrative privileges. One needs to create a password files before remote administrators (like OEM) will be allowed to connect.
Follow this procedure to create a new password file:
. Log in as the Oracle software owner
. Runcommand: orapwd file=$ORACLE_HOME/dbs/orapw$ORACLE_SID password=mypasswd
. Shutdown the database (SQLPLUS> SHUTDOWN IMMEDIATE)
. Edit the INIT.ORA file and ensure REMOTE_LOGIN_PASSWORDFILE=exclusive is set.
. Startup the database (SQLPLUS> STARTUP)
NOTE: The orapwd utility presents a security risk in that it receives a password from the command line. This password is visible in the process table of many systems. Administrators needs to be aware of this!

Is it possible to modify an external query in a report which contains it?

Does a grouping done for objects in the layout editor affect the grouping done in the data model editor?

How does one add users to a password file? (for DBA )
One can select from the SYS.V_$PWFILE_USERS view to see which users are listed in the password file. New users can be added to the password file by granting them SYSDBA or SYSOPER privileges, or by using the orapwd utility. GRANT SYSDBA TO scott;

If a break order is set on a column would it affect columns which are under the column?

Why are OPS$ accounts a security risk in a client/server environment? (for DBA )
If you allow people to log in with OPS$ accounts from Windows Workstations, you cannot be sure who they really are. With terminals, you can rely on operating system passwords, with Windows, you cannot.
If you set REMOTE_OS_AUTHENT=TRUE in your init.ora file, Oracle assumes that the remote OS has authenticated the user. If REMOTE_OS_AUTHENT is set to FALSE (recommended), remote users will be unable to connect without a password. IDENTIFIED EXTERNALLY will only be in effect from the local host. Also, if you are using "OPS$" as your prefix, you will be able to log on locally with or without a password, regardless of whether you have identified your ID with a password or defined it to be IDENTIFIED EXTERNALLY.

Do user parameters appear in the data modal editor in 2.5?

Can you pass data parameters to forms?

Is it possible to link two groups inside a cross products after the cross products group has been created?

What are the different modals of windows?
Modalless windows
Modal windows

What are modal windows?
Modal windows are usually used as dialogs, and have restricted functionality compared to modelless windows. On some platforms for example operators cannot resize, scroll or iconify a modal window.

What are the different default triggers created when Master Deletes Property is set to Non-isolated?

Master Deletes Property Resulting Triggers
Non-Isolated(the default) On-Check-Delete-Master

What are the different default triggers created when Master Deletes Property is set to isolated?

Master Deletes Property Resulting Triggers
Isolated On-Clear-Details

What are the different default triggers created when Master Deletes Property is set to Cascade?

Master Deletes Property Resulting Triggers
Cascading On-Clear-Details

What is the diff. bet. setting up of parameters in reports 2.0 reports2.5?
LOVs can be attached to parameters in the reports 2.5 parameter form.

What are the difference between lov & list item?
Lov is a property where as list item is an item. A list item can have only one column, lov can have one or more columns

What is the advantage of the library?
Libraries provide a convenient means of storing client-side program units and sharing them among multiple applications. Once you create a library, you can attach it to any other form, menu, or library modules. When you can call library program units from triggers menu items commands and user named routine, you write in the modules to which you have attach the library. When a library attaches another library, program units in the first library can reference program units in the attached library. Library support dynamic loading-that is library program units are loaded into an application only when needed. This can significantly reduce the run-time memory requirements of applications.

What is lexical reference? How can it be created?
Lexical reference is place_holder for text that can be embedded in a sql statements. A lexical reference can be created using & before the column or parameter name.

What is system.coordination_operation?
It represents the coordination causing event that occur on the master block in master-detail relation.

What is synchronize?
It is a terminal screen with the internal state of the form. It updates the screen display to reflect the information that oracle forms has in its internal representation of the screen.

What use of command line parameter cmd file?
It is a command line argument that allows you to specify a file that contain a set of arguments for r20run.

What is a Text_io Package?
It allows you to read and write information to a file in the file system.

What is forms_DDL?
Issues dynamic Sql statements at run time, including server side pl/SQl and DDL

How is link tool operation different bet. reports 2 & 2.5?
In Reports 2.0 the link tool has to be selected and then two fields to be linked are selected and the link is automatically created. In 2.5 the first field is selected and the link tool is then used to link the first field to the second field.

What are the different styles of activation of ole Objects?
In place activationExternal activation

How do you reference a Parameter?
In Pl/Sql, You can reference and set the values of form parameters using bind variables syntax. Ex. PARAMETER name = '' or :block.item = PARAMETER Parameter name

What is the difference between object embedding & linking in Oracle forms?
In Oracle forms, Embedded objects become part of the form module, and linked objects are references from a form module to a linked source file.

Name of the functions used to get/set canvas properties?
Get_view_property, Set_view_property

What are the built-ins that are used for setting the LOV properties at runtime?

What are the built-ins used for processing rows?

What are built-ins used for Processing rows?

What are the built-in used for getting cell values?

What are the built-ins used for Getting cell values?

Atleast how many set of data must a data model have before a data model can be base on it?

To execute row from being displayed that still use column in the row which property can be used?
Format trigger.

What are different types of modules available in oracle form?
Form module - a collection of objects and code routines Menu modules - a collection of menus and menu item commands that together make up an application menu library module - a collection of user named procedures, functions and packages that can be called from other modules in the application

What is the remove on exit property?
For a modelless window, it determines whether oracle forms hides the window automatically when the operators navigates to an item in the another window.

What is WHEN-Database-record trigger?
Fires when oracle forms first marks a record as an insert or an update. The trigger fires as soon as oracle forms determines through validation that the record should be processed by the next post or commit as an insert or update. c generally occurs only when the operators modifies the first item in the record, and after the operator attempts to navigate out of the item.

What is a difference between pre-select and pre-query?
Fires during the execute query and count query processing after oracle forms constructs the select statement to be issued, but before the statement is actually issued. The pre-query trigger fires just before oracle forms issues the select statement to the database after the operator as define the example records by entering the query criteria in enter query mode.Pre-query trigger fires before pre-select trigger.

What are built-ins associated with timers?

What are the built-ins used for finding object ID functions?

What are the built-ins used for finding Object ID function?

Any attempt to navigate programmatically to disabled form in a call_form stack is allowed?

Use the Add_group_row procedure to add a row to a static record group 1. true or false?

What third party tools can be used with Oracle EBU/ RMAN? (for DBA)
The following Media Management Software Vendors have integrated their media management software packages with Oracle Recovery Manager and Oracle7 Enterprise Backup Utility. The Media Management Vendors will provide first line technical support for the integrated backup/recover solutions.
Veritas NetBackup
EMC Data Manager (EDM)
IBM's Tivoli Storage Manager - formerly ADSM
Legato Networker
ManageIT Backup and Recovery
Sterling Software's SAMS:Alexandria - formerly from Spectralogic
Sun Solstice Backup

Why and when should one tune? (for DBA)
One of the biggest responsibilities of a DBA is to ensure that the Oracle database is tuned properly. The Oracle RDBMS is highly tunable and allows the database to be monitored and adjusted to increase its performance. One should do performance tuning for the following reasons:
The speed of computing might be wasting valuable human time (users waiting for response); Enable your system to keep-up with the speed business is conducted; and Optimize hardware usage to save money (companies are spending millions on hardware). Although this FAQ is not overly concerned with hardware issues, one needs to remember than you cannot tune a Buick into a Ferrari.

How can a break order be created on a column in an existing group? What are the various sub events a mouse double click event involves?
By dragging the column outside the group.

What is the use of place holder column? What are the various sub events a mouse double click event involves?
A placeholder column is used to hold calculated values at a specified place rather than allowing is to appear in the actual row where it has to appear.

What is the use of hidden column? What are the various sub events a mouse double click event involves?
A hidden column is used to when a column has to embed into boilerplate text.

What database aspects should be monitored? (for DBA)
One should implement a monitoring system to constantly monitor the following aspects of a database. Writing custom scripts, implementing Oracle's Enterprise Manager, or buying a third-party monitoring product can achieve this. If an alarm is triggered, the system should automatically notify the DBA (e-mail, page, etc.) to take appropriate action.
Infrastructure availability:
. Is the database up and responding to requests
. Are the listeners up and responding to requests
. Are the Oracle Names and LDAP Servers up and responding to requests
. Are the Web Listeners up and responding to requests

Things that can cause service outages:
. Is the archive log destination filling up?
. Objects getting close to their max extents
. User and process limits reached

Things that can cause bad performance:
See question "What tuning indicators can one use?".

Where should the tuning effort be directed? (for DBA)
Consider the following areas for tuning. The order in which steps are listed needs to be maintained to prevent tuning side effects. For example, it is no good increasing the buffer cache if you can reduce I/O by rewriting a SQL statement. Database Design (if it's not too late):
Poor system performance usually results from a poor database design. One should generally normalize to the 3NF. Selective denormalization can provide valuable performance improvements. When designing, always keep the "data access path" in mind. Also look at proper data partitioning, data replication, aggregation tables for decision support systems, etc.
Application Tuning:
Experience showed that approximately 80% of all Oracle system performance problems are resolved by coding optimal SQL. Also consider proper scheduling of batch tasks after peak working hours.
Memory Tuning:
Properly size your database buffers (shared pool, buffer cache, log buffer, etc) by looking at your buffer hit ratios. Pin large objects into memory to prevent frequent reloads.
Disk I/O Tuning:
Database files needs to be properly sized and placed to provide maximum disk subsystem throughput. Also look for frequent disk sorts, full table scans, missing indexes, row chaining, data fragmentation, etc
Eliminate Database Contention:
Study database locks, latches and wait events carefully and eliminate where possible. Tune the Operating System:
Monitor and tune operating system CPU, I/O and memory utilization. For more information, read the related Oracle FAQ dealing with your specific operating system.

What are the various sub events a mouse double click event involves? What are the various sub events a mouse double click event involves?
Double clicking the mouse consists of the mouse down, mouse up, mouse click, mouse down & mouse up events.

What are the default parameter that appear at run time in the parameter screen? What are the various sub events a mouse double click event involves?
Destype and Desname.

What are the built-ins used for Creating and deleting groups?
CREATE-GROUP (function)

What are different types of canvas views?
Content canvas views
Stacked canvas views
Horizontal toolbar
vertical toolbar.

What are the different types of Delete details we can establish in Master-Details?

What is relation between the window and canvas views?
Canvas views are the back ground objects on which you place the interface items (Text items), check boxes, radio groups etc.,) and boilerplate objects (boxes, lines, images etc.,) that operators interact with us they run your form . Each canvas views displayed in a window.

What is a User_exit?
Calls the user exit named in the user_exit_string. Invokes a 3Gl program by name which has been properly linked into your current oracle forms executable. 

How is it possible to select generate a select set for the query in the query property sheet?
By using the tables/columns button and then specifying the table and the column names.

How can values be passed bet. precompiler exits & Oracle call interface?
By using the statement EXECIAFGET & EXECIAFPUT.

How can a square be drawn in the layout editor of the report writer?
By using the rectangle tool while pressing the (Constraint) key.

How can a text file be attached to a report while creating in the report writer?
By using the link file property in the layout boiler plate property sheet.

How can I message to passed to the user from reports?
By using SRW.MESSAGE function.

Does one need to drop/ truncate objects before importing? (for DBA)
Before one import rows into already populated tables, one needs to truncate or drop these tables to get rid of the old data. If not, the new data will be appended to the existing tables. One must always DROP existing Sequences before re-importing. If the sequences are not dropped, they will generate numbers inconsistent with the rest of the database. Note: It is also advisable to drop indexes before importing to speed up the import process. Indexes can easily be recreated after the data was successfully imported.

How can a button be used in a report to give a drill down facility?
By setting the action associated with button to Execute pl/sql option and using the SRW.Run_report function.

Can one import/export between different versions of Oracle? (for DBA)
Different versions of the import utility is upwards compatible. This means that one can take an export file created from an old export version, and import it using a later version of the import utility. This is quite an effective way of upgrading a database from one release of Oracle to the next.
Oracle also ships some previous catexpX.sql scripts that can be executed as user SYS enabling older imp/exp versions to work (for backwards compatibility). For example, one can run $ORACLE_HOME/rdbms/admin/catexp7.sql on an Oracle 8 database to allow the Oracle 7.3 exp/imp utilities to run against an Oracle 8 database.

What are different types of images?
Boiler plate imagesImage Items

Can one export to multiple files?/ Can one beat the Unix 2 Gig limit? (for DBA)
From Oracle8i, the export utility supports multiple output files. This feature enables large exports to be divided into files whose sizes will not exceed any operating system limits (FILESIZE= parameter). When importing from multi-file export you must provide the same filenames in the same sequence in the FILE= parameter. Look at this example:
exp SCOTT/TIGER FILE=D:\F1.dmp,E:\F2.dmp FILESIZE=10m LOG=scott.log
Use the following technique if you use an Oracle version prior to 8i:
Create a compressed export on the fly. Depending on the type of data, you probably can export up to 10 gigabytes to a single file. This example uses gzip. It offers the best compression I know of, but you can also substitute it with zip, compress or whatever.
# create a named pipe
mknod exp.pipe p
# read the pipe - output to zip file in the background
gzip <> scott.exp.gz &
# feed the pipe
exp userid=scott/tiger file=exp.pipe ...

What is bind reference and how can it be created?
Bind reference are used to replace the single value in sql, pl/sql statements a bind reference can be created using a (:) before a column or a parameter name.

How can one improve Import/ Export performance? (for DBA)
. Set the BUFFER parameter to a high value (e.g. 2M)
. Set the RECORDLENGTH parameter to a high value (e.g. 64K)
. Stop unnecessary applications to free-up resources for your job.
. If you run multiple export sessions, ensure they write to different physical disks.
. DO NOT export to an NFS mounted filesystem. It will take forever.

. Create an indexfile so that you can create indexes AFTER you have imported data. Do this by setting INDEXFILE to a filename and then import. No data will be imported but a file containing index definitions will be created. You must edit this file afterwards and supply the passwords for the schemas on all CONNECT statements.
. Place the file to be imported on a separate physical disk from the oracle data files
. Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) considerably in the init$SID.ora file
. Set the LOG_BUFFER to a big value and restart oracle.
. Stop redo log archiving if it is running (ALTER DATABASE NOARCHIVELOG;)
. Create a BIG tablespace with a BIG rollback segment inside. Set all other rollback segments offline (except the SYSTEM rollback segment of course). The rollback segment must be as big as your biggest table (I think?)
. Use COMMIT=N in the import parameter file if you can afford it
. Use ANALYZE=N in the import parameter file to avoid time consuming ANALYZE statements
. Remember to run the indexfile previously created

Give the sequence of execution of the various report triggers?
Before form , After form , Before report, Between page, After report.

What are the common Import/ Export problems? (for DBA )
ORA-00001: Unique constraint (...) violated - You are importing duplicate rows. Use IGNORE=NO to skip tables that already exist (imp will give an error if the object is re-created).
ORA-01555: Snapshot too old - Ask your users to STOP working while you are exporting or use parameter CONSISTENT=NO
ORA-01562: Failed to extend rollback segment - Create bigger rollback segments or set parameter COMMIT=Y while importing
IMP-00015: Statement failed ... object already exists... - Use the IGNORE=Y import parameter to ignore these errors, but be careful as you might end up with duplicate rows.

Why is it preferable to create a fewer no. of queries in the data model?
Because for each query, report has to open a separate cursor and has to rebind, execute and fetch data.