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?
Previewer


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?
On-Check_delete_masterOn_clear_detailsOn_populate_details


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?
No.


Does a grouping done for objects in the layout editor affect the grouping done in the data model editor?
No.


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?
No


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?
No


Can you pass data parameters to forms?
No


Is it possible to link two groups inside a cross products after the cross products group has been created?
no


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
On-Clear-Details
On-Populate-Details

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

Master Deletes Property Resulting Triggers
---------------------------------------------------
Isolated On-Clear-Details
On-Populate-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
On-Populate-Details
Pre-delete


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?
get_lov_property
set_lov_property


What are the built-ins used for processing rows?
Get_group_row_count(function)
Get_group_selection_count(function)
Get_group_selection(function)
Reset_group_selection(procedure)
Set_group_selection(procedure)
Unset_group_selection(procedure)


What are built-ins used for Processing rows?
GET_GROUP_ROW_COUNT(function)
GET_GROUP_SELECTION_COUNT(function)
GET_GROUP_SELECTION(function)
RESET_GROUP_SELECTION(procedure)
SET_GROUP_SELECTION(procedure)
UNSET_GROUP_SELECTION(procedure)


What are the built-in used for getting cell values?
Get_group_char_cell(function)
Get_groupcell(function)
Get_group_number_cell(function)

What are the built-ins used for Getting cell values?
GET_GROUP_CHAR_CELL (function)
GET_GROUPCELL(function)
GET_GROUP_NUMBET_CELL(function)

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

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?
find_timercreate_timerdelete_timer


What are the built-ins used for finding object ID functions?
Find_group(function)
Find_column(function)


What are the built-ins used for finding Object ID function?
FIND_GROUP(function)
FIND_COLUMN(function)

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

Use the Add_group_row procedure to add a row to a static record group 1. true or false?
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)
HP OMNIBack II
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)
CREATE_GROUP_FROM_QUERY(function)
DELETE_GROUP(procedure)


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?
Cascade
Isolate
Non-isolate


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)
EXPORT:
. 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.

IMPORT:
. 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.

Oracle Forms 4.0 Interview Questions and Answers

Give the Types of modules in a form?
    - Form
- Menu
- Library

2.     Write the Abbreviation for the following File Extension
    1. FMB
2. MMB
3. PLL

FMB ----- Form Module Binary.
MMB ----- Menu Module Binary.
PLL ------ PL/SQL Library Module Binary.

3.     What are the design facilities available in forms 4.0?
    Default Block facility.
Layout Editor.
Menu Editor.
Object Lists.
Property Sheets.
PL/SQL Editor.
Tables Columns Browser.
Built-ins Browser.

4.     What is a Layout Editor?
    The Layout Editor is a graphical design facility for creating and arranging items and boilerplate text and graphics objects in your application's interface.

5.     What do you mean by a block in forms4.0?
    Block is a single mechanism for grouping related items into a functional unit for storing,displaying and manipulating records.
6.     Explain types of Block in forms4.0?
    Base table Blocks.
Control Blocks.
1. A base table block is one that is associated with a specific database table or view.
2. A control block is a block that is not associated with a database table.

7.     What are the options available to refresh snapshots?
    COMPLETE - Tables are completely regenerated using the snapshot's query and the master tables every time the snapshot referenced.
FAST - If simple snapshot used then a snapshot log can be used to send the changes to the snapshot  tables.
FORCE - Default value. If possible it performs a FAST refresh; Otherwise it will perform a complete refresh.

8.     List the Types of tems?
    Text item.
Chart item.
Check box.
Display item.
Image item.
List item.
Radio Group.
User Area item.

9.     What is a Navigable item?
    A navigable item is one that operators can navigate to with the keyboard during default navigation, or that Oracle forms can navigate to by executing a navigational
built-in procedure.

10.     Can you change the color of the push button in design time?
    No.

11.     What is a Check Box?
      A Check Box is a two state control that indicates whether a certain condition or value is on or off, true or false. The display state of a check box is always either "checked" or "unchecked".

12.     What are the triggers associated with a check box?
    Only When-checkbox-activated Trigger associated with a Check box.

13.     What is a display item?
    Display items are similar to text items but store only fetched or assigned values. Operators cannot navigate to a display item or edit the value it contains.

14.     What is a list item?
    It is a list of text elements.

15.     What are the display styles of list items?
    Poplist, No text Item displayed in the list item.
Tlist, No element in the list is highlighted.

16.     What is a radio Group?
    Radio groups display a fixed no of options that are mutually exclusive. User can select one out of n number of options.

17.     How many maximum number of radio buttons can you assign to a radio group?
    Unlimited no of radio buttons can be assigned to a radio group

18.     Can you change the default value of the radio button group at run time?
    No.

19.     What triggers are associated with the radio group?
    Only when-radio-changed trigger associated with radio group

20.     What is a visual attribute?
    Visual Attributes are the font, color and pattern characteristics of objects that operators see and intract with in our application.

21.     What are the types of visual attribute settings?
    Custom Visual attributes
Default visual attributes
Named Visual attributes.

22.     What is a window?
    A window, byitself, can be thought of as an empty frame. The frame provides a way to intract with the window, including the ability to scroll, move, and resize the window. The content of the window ie. what is displayed inside the frame is determined by the canvas
View or canvas-views displayed in the window at run-time.

23.     What are the differrent types of windows?
    Root window,
Secondary window.

24.     Can a root window be made modal?
    No.

25.     List the buil-in routine for controlling window during run-time?
    Find_window,
get_window_property,
hide_window,
move_window,
resize_window,
set_window_property,
show_View

26.     List the windows event triggers available in Forms 4.0?
    When-window-activated, when-window-closed, when-window-deactivated, when-window-resized

27.     What built-in is used for changing the properties of the window dynamically?
    Set_window_property

28.     What is a canvas-view?
    A canvas-view is the background object on which you layout the interface items (text-items, check boxes, radio groups, and so on.) and boilerplate objects that operators see and interact with as they run your form. At run-time, operators can see only those items that have been assiged to a specific canvas. Each canvas, in term, must be displayed in a specfic window.

29.     Give the equivalent term in forms 4.0 for the following.
Page, Page 0?
    Page - Canvas-View
Page 0 - Canvas-view null.

30.     What are the types of canvas-views?
    Content View, Stacked View.

31.     What is the content view and stacked view?
    A content view is the "Base" view that occupies the entire content pane of the window in which it is displayed.
A stacked view differs from a content canvas view in that it is not the base view for the window to which it is assigned

32.     List the built-in routines for the controlling canvas views during run-time?
    Find_canvas
Get-Canvas_property
Get_view_property
Hide_View
Replace_content_view
Scroll_view
Set_canvas_property
Set_view_property
Show_view

33.     What is an Alert?
    An alert is a modal window that displays a message notifies the operator of some application condition

34.     What are the display styles of an alert?
    Stop, Caution, note

35.     Can you attach an alert to a field?
    No

36.     What built-in is used for showing the alert during run-time?
    Show_alert.

37.     Can you change the alert messages at run-time? If yes, give the name of th built-in to chage the alert messages at run-time.
    Yes.
Set_alert_property.

40.     What is the built-in function used for finding the alert?
    Find_alert

41.     List the editors availables in forms 4.0?
    Default editor
User_defined editors
system editors.

42.     What built-in routines are used to display editor dynamicaly?
    Edit_text item
show_editor

43.     What is a Lov?
    A list of values is a single or multi column selection list displayed in a pop-up window

44.     Can you attach a lov to a field at design time?
    Yes.

45.     Can you attach a lov to a field at run-time? If yes, give the build-in name.
    Yes.
Set_item_proprety

46.     What is the built-in used for showing lov at runtime?
    Show_lov

47.     What is the built-in used to get and set lov properties during run-time?
    Get_lov_property
Set_lov_property

48.     What is a record Group?
    A record group is an internal oracle forms data structure that has a simillar column/row frame work to a database table

49.     What are the different types of a record group?
    Query record group
Static record group
Non query record group

50.     Give built-in routine related to record groups?
    Create_group (Function)
Create_group_from_query(Function)
Delete_group(Procedure)
Add_group_column(Function)
Add_group_row(Procedure)
Delete_group_row(Procedure)
Populate_group(Function)
Populate_group_with_query(Function)
Set_group_Char_cell(procedure)

51.     What is the built_in routine used to count the no of rows in a group?
    Get_group _row_count

52.     List system variables available in forms 4.0, and not available in forms 3.0?
    System.cordination_operation
System Date_threshold
System.effective_Date
System.event_window
System.suppress_working

53.     System.effective_date system variable is read only True/False
    False

54.     What is a library in Forms 4.0?
    A library is a collection of Pl/SQL program units, including user named procedures, functions & packages

55.     Is it possible to attach same library to more than one form?
    Yes

56.     Explain the following file extention related to library?
    .pll,.lib,.pld
The library pll files is a portable design file comparable to an fmb form file
The library lib file is a plat form specific, generated library file comparable to an fmx form file
The pld file is Txt format file and can be used for source controlling your library files

57.     How do you pass the parameters from one form to another form?
    To pass one or more parameters to a called form, the calling form must perform the following steps in a trigger or user named routine excute the create_parameter_list built_in function to programatically.
Create a parameter list to execute the add parameter built_in procedure to add one or more parameters list.
Execute the call_form, New_form or run_product built_in procedure and include the name or id of the parameter list to be passed to the called form.

58.     What are the built-in routines is available in forms 4.0 to create and manipulate a parameter list?
    Add_parameter
Create_Parameter_list
Delete_parameter
Destroy_parameter_list
Get_parameter_attr
Get_parameter_list
set_parameter_attr

59.     What are the two ways to incorporate images into a oracle forms application?
    Boilerplate Images
Image_items

60.     How image_items can be populate to field in forms 4.0?
    A fetch from a long raw database column PL/Sql assignment to executing the read_image_file built_in procedure to get an image from the file system.

61.     What are the triggers associated with the image item?
    When-Image-activated(Fires when the operator double clicks on an image Items)
When-image-pressed(fires when the operator selects or deselects the image item)

62.     List some built-in routines used to manipulate images in image_item?
    Image_add
Image_and
Image_subtract
Image_xor
Image_zoom

63.     What are the built_in used to trapping errors in forms 4?
    Error_type return character
Error_code return number
Error_text return char
Dbms_error_code return no.
Dbms_error_text return char

64.     What is a predefined exception available in forms 4.0?
    Raise form_trigger_failure

65.     What are the menu items that oracle forms 4.0 supports?
    Plain, Check,Radio, Separator, Magic

Tuesday, February 18, 2014

ORACLE SQL PL/SQL Interview Questions


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What are the various types of queries ?
Answer: The types of queries are:
Normal Queries
Sub Queries
Co-related queries
Nested queries
Compound queries
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What is a transaction ?
Answer: A transaction is a set of SQL statements between any two COMMIT and ROLLBACK statements.
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What is implicit cursor and how is it used by Oracle ?
Answer: An implicit cursor is a cursor which is internally created by Oracle.It is created by Oracle for each individual SQL.
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Which of the following is not a schema object : Indexes, tables, public synonyms, triggers and packages ?
Answer: Public synonyms
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What is PL/SQL?
Answer: PL/SQL is Oracle's Procedural Language extension to SQL.The language includes object oriented programming techniques such as encapsulation, function overloading, information hiding (all but inheritance), and so, brings state-of-the-art programming to the Oracle database server and a variety of Oracle tools.
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Is there a PL/SQL Engine in SQL*Plus?
Answer: No.Unlike Oracle Forms, SQL*Plus does not have a PL/SQL engine.Thus, all your PL/SQL are send directly to the database engine for execution.This makes it much more efficient as SQL statements are not stripped off and send to the database individually.
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Is there a limit on the size of a PL/SQL block?
Answer: Currently, the maximum parsed/compiled size of a PL/SQL block is 64K and the maximum code size is 100K.You can run the following select statement to query the size of an existing package or procedure. SQL> select * from dba_object_size where name = 'procedure_name'
 
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Can one read/write files from PL/SQL?
Answer: Included in Oracle 7.3 is a UTL_FILE package that can read and write files.The directory you intend writing to has to be in your INIT.ORA file (see UTL_FILE_DIR=...parameter).
Before Oracle 7.3 the only means of writing a file was to use DBMS_OUTPUT with the SQL*Plus SPOOL command.
DECLARE
fileHandler UTL_FILE.FILE_TYPE;
BEGIN
fileHandler := UTL_FILE.FOPEN('/home/oracle/tmp', 'myoutput','W');
UTL_FILE.PUTF(fileHandler, 'Value of func1 is %sn', func1(1));
UTL_FILE.FCLOSE(fileHandler);
END;
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How can I protect my PL/SQL source code?
Answer: PL/SQL V2.2, available with Oracle7.2, implements a binary wrapper for PL/SQL programs to protect the source code.This is done via a standalone utility that transforms the PL/SQL source code into portable binary object code (somewhat larger than the original).This way you can distribute software without having to worry about exposing your proprietary algorithms and methods.SQL*Plus and SQL*DBA will still understand and know how to execute such scripts.Just be careful, there is no "decode" command available. The syntax is:                      wrap name=myscript.sql
oname=xxxx.yyy
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Can one use dynamic SQL within PL/SQL? OR Can you use a DDL in a procedure ? How ?
Answer: From PL/SQL V2.1 one can use the DBMS_SQL package to execute dynamic SQL statements.
Eg: CREATE OR REPLACE PROCEDURE DYNSQL AS
cur integer;
rc integer;
BEGIN
cur := DBMS_SQL.OPEN_CURSOR;
DBMS_SQL.PARSE(cur,'CREATE TABLE X (Y DATE)',
DBMS_SQL.NATIVE);
rc := DBMS_SQL.EXECUTE(cur);
DBMS_SQL.CLOSE_CURSOR(cur);
END;
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What are the various types of Exceptions ?
Answer: User defined and Predefined Exceptions.
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Can we define exceptions twice in same block ?
Answer: No.
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What is the difference between a procedure and a function ?
Answer: Functions return a single variable by value whereas procedures do not return any variable by value.Rather they return multiple variables by passing variables by reference through their OUT parameter.
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Can you have two functions with the same name in a PL/SQL block ?
Answer: Yes.
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Can you have two stored functions with the same name ?
Answer: Yes.
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Can you call a stored function in the constraint of a table ?
Answer: No.
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What are the various types of parameter modes in a procedure ?
Answer: IN, OUT AND INOUT.
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What is Over Loading and what are its restrictions ?
Answer: OverLoading means an object performing different functions depending upon the no.of parameters or the data type of the parameters passed to it.
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Can functions be overloaded ?
Answer: Yes.
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Can 2 functions have same name & input parameters but differ only by return datatype
Answer: No.
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What are the constructs of a procedure, function or a package ?
Answer: The constructs of a procedure, function or a package are :
variables and constants
cursors
exceptions
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Why Create or Replace and not Drop and recreate procedures ?
Answer: So that Grants are not dropped.
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Can you pass parameters in packages ? How ?
Answer: Yes.You can pass parameters to procedures or functions in a package.
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What are the parts of a database trigger ?
Answer: The parts of a trigger are:
A triggering event or statement
A trigger restriction
A trigger action
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What are the various types of database triggers ?
Answer: There are 12 types of triggers, they are combination of :
Insert, Delete and Update Triggers.
Before and After Triggers.
Row and Statement Triggers.
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What is the advantage of a stored procedure over a database trigger ?
Answer: We have control over the firing of a stored procedure but we have no control over the firing of a trigger.
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What is the maximum no.of statements that can be specified in a trigger statement ?
Answer: One.
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Can views be specified in a trigger statement ?
Answer: No
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What are the values of :new and :old in Insert/Delete/Update Triggers ?
Answer: INSERT : new = new value, old = NULL
DELETE : new = NULL, old = old value
UPDATE : new = new value, old = old value
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What are cascading triggers? What is the maximum no of cascading triggers at a time?
Answer: When a statement in a trigger body causes another trigger to be fired, the triggers are said to be cascading.Max = 32.
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What are mutating triggers ?
Answer: A trigger giving a SELECT on the table on which the trigger is written.
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What are constraining triggers ?
Answer: A trigger giving an Insert/Updat e on a table having referential integrity constraint on the triggering table.
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Describe Oracle database's physical and logical structure ?
Answer:
Physical : Data files, Redo Log files, Control file.
Logical : Tables, Views, Tablespaces, etc.
 
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Can you increase the size of a tablespace ? How ?
Answer: Yes, by adding datafiles to it.
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Can you increase the size of datafiles ? How ?
Answer: No (for Oracle 7.0)
Yes (for Oracle 7.3 by using the Resize clause )
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What is the use of Control files ?
Answer: Contains pointers to locations of various data files, redo log files, etc.
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What is the use of Data Dictionary ?
Answer: It Used by Oracle to store information about various physical and logical Oracle structures e.g.Tables, Tablespaces, datafiles, etc
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What are the advantages of clusters ?
Answer: Access time reduced for joins.
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What are the disadvantages of clusters ?
Answer: The time for Insert increases.
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Can Long/Long RAW be clustered ?
Answer: No.
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Can null keys be entered in cluster index, normal index ?
Answer: Yes.
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Can Check constraint be used for self referential integrity ? How ?
Answer: Yes.In the CHECK condition for a column of a table, we can reference some other column of the same table and thus enforce self referential integrity.
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What are the min.extents allocated to a rollback extent ?
Answer: Two
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What are the states of a rollback segment ? What is the difference between partly available and needs recovery ?
Answer: The various states of a rollback segment are :
ONLINE
OFFLINE
PARTLY AVAILABLE
NEEDS RECOVERY
INVALID.
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What is the difference between unique key and primary key ?
Answer: Unique key can be null; Primary key cannot be null.
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An insert statement followed by a create table statement followed by rollback ? Will the rows be inserted ?
Answer: No.
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Can you define multiple savepoints ?
Answer: Yes.
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Can you Rollback to any savepoint ?
Answer: Yes.
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What is the maximum no.of columns a table can have ?
Answer: 254.
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What is the significance of the & and && operators in PL SQL ?
Answer: The & operator means that the PL SQL block requires user input for a variable.The && operator means that the value of this variable should be the same as inputted by the user previously for this same variable
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Can you pass a parameter to a cursor ?
Answer: Explicit cursors can take parameters, as the example below shows.A cursor parameter can appear in a query wherever a constant can appear.
CURSOR c1 (median IN NUMBER) IS
SELECT job, ename FROM emp WHERE sal > median;
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What are the various types of RollBack Segments ?
Answer: The types of Rollback sagments are as follows :
Public Available to all instances
Private Available to specific instance
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Can you use %RowCount as a parameter to a cursor ?
Answer: Yes
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Is the query below allowed :
Select sal, ename Into x From emp Where ename = 'KING' (Where x is a record of Number(4) and Char(15))
Answer: Yes
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Is the assignment given below allowed :
ABC = PQR (Where ABC and PQR are records)
Answer: Yes
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Is this for loop allowed : For x in &Start..&End Loop
Answer: Yes
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How many rows will the following SQL return : Select * from emp Where rownum < 10;
Answer: 9 rows
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How many rows will the following SQL return : Select * from emp Where rownum = 10;
Answer: No rows
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Which symbol preceeds the path to the table in the remote database ?
Answer: @
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Are views automatically updated when base tables are updated ?
Answer: Yes
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Can a trigger written for a view ?
Answer: No
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If all the values from a cursor have been fetched and another fetch is issued, the output will be : error, last record or first record ?
Answer: Last Record
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A table has the following data : [[5, Null, 10]].What will the average function return ?
Answer: 7.5
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Is Sysdate a system variable or a system function?
Answer: System Function
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Consider a sequence whose currval is 1 and gets incremented by 1 by using the nextval reference we get the next number 2.Suppose at this point we issue an rollback and again issue a nextval.What will the output be ?
Answer: 3
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Definition of relational DataBase by Dr.Codd (IBM)?
Answer: A Relational Database is a database where all data visible to the user is organized strictly as tables of data values and where all database operations work on these tables.
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What is Multi Threaded Server (MTA) ?
Answer: In a Single Threaded Architecture (or a dedicated server configuration) the database manager creates a separate process for each database user.But in MTA the database manager can assign multiple users (multiple user processes) to a single dispatcher (server process), a controlling process that queues request for work thus reducing the databases memory requirement and resources.
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Which are initial RDBMS, Hierarchical & N/w database ?
Answer:
RDBMS - R system
Hierarchical - IMS
N/W - DBTG
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Difference between Oracle 6 and Oracle 7
Answer:
ORACLE 7                                 ORACLE 6  Cost based optimizer                   Rule based optimizer 
Shared SQL Area                        SQL area allocated for each user 
Multi Threaded Server                  Single Threaded Server 
Hash Clusters                             Only B-Tree indexing 
Roll back Size                            Adjustment No provision 
Truncate command                      No provision 
Distributed Database                   Distributed Query 
Table replication & snapshots       No provision 
Client/Server Tech                       No provision 
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What is Functional Dependency?
Answer: Given a relation R, attribute Y of R is functionally dependent on attribute X of R if and only if each X-value has associated with it precisely one -Y value in R
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What is Auditing ?
Answer: The database has the ability to audit all actions that take place within it. a) Login attempts, b) Object Accesss, c) Database Action Result of Greatest(1,NULL) or Least(1,NULL) NULL
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While designing in client/server what are the 2 imp.things to be considered ?
Answer: Network Overhead (traffic), Speed and Load of client server
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What are the disadvantages of SQL ?
Answer: Disadvantages of SQL are :
Cannot drop a field
Cannot rename a field
Cannot manage memory
Procedural Language option not provided
Index on view or index on index not provided
View updation problem
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When to create indexes ?
Answer: To be created when table is queried for less than 2% or 4% to 25% of the table rows.
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How can you avoid indexes ?
Answer: To make index access path unavailable Use FULL hint to optimizer for full table scan Use INDEX or AND-EQUAL hint to optimizer to use one index or set to indexes instead of another. Use an expression in the Where Clause of the SQL.
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What is the result of the following SQL : Select 1 from dual UNION Select 'A' from dual;
Answer: Error
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Can database trigger written on synonym of a table and if it can be then what would be the effect if original table is accessed.
Answer: Yes, database trigger would fire.
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Can you alter synonym of view or view ?
Answer: No
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Can you create index on view
Answer: No.
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What is the difference between a view and a synonym ?
Answer: Synonym is just a second name of table used for multiple link of database.View can be created with many tables, and with virtual columns and with conditions.But synonym can be on view.
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What's the length of SQL integer ?
Answer: 32 bit length
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What is the difference between foreign key and reference key ?
Answer: Foreign key is the key i.e.attribute which refers to another table primary key. Reference key is the primary key of table referred by another table.
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Can dual table be deleted, dropped or altered or updated or inserted ?
Answer: Yes
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If content of dual is updated to some value computation takes place or not ?
Answer: Yes
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If any other table same as dual is created would it act similar to dual?
Answer: Yes
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For which relational operators in where clause, index is not used ?
Answer: <> , like '%...' is NOT functions, field +constant, field||''
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Assume that there are multiple databases running on one machine.How can you switch from one to another ?
Answer: Changing the ORACLE_SID
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What are the advantages of Oracle ?
Answer: Portability : Oracle is ported to more platforms than any of its competitors, running on more than 100 hardware platforms and 20 networking protocols. Market Presence : Oracle is by far the largest RDBMS vendor and spends more on R & D than most of its competitors earn in total revenue.This market clout means that you are unlikely to be left in the lurch by Oracle and there are always lots of third party interfaces available. Backup and Recovery : Oracle provides industrial strength support for on-line backup and recovery and good software fault tolerence to disk failure.You can also do point-in-time recovery. Performance : Speed of a 'tuned' Oracle Database and application is quite good, even with large databases.Oracle can manage > 100GB databases. Multiple database support : Oracle has a superior ability to manage multiple databases within the same transaction using a two-phase commit protocol.
 
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What is a forward declaration ? What is its use ?
Answer: PL/SQL requires that you declare an identifier before using it.Therefore, you must declare a subprogram before calling it.This declaration at the start of a subprogram is called forward declaration.A forward declaration consists of a subprogram specification terminated by a semicolon.
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What are actual and formal parameters ?
Answer: Actual Parameters : Subprograms pass information using parameters.The variables or expressions referenced in the parameter list of a subprogram call are actual parameters.For example, the following procedure call lists two actual parameters named emp_num and amount:
Eg.raise_salary(emp_num, amount);Formal Parameters : The variables declared in a subprogram specification and referenced in the subprogram body are formal parameters.For example, the following procedure declares two formal parameters named emp_id and increase:
Eg.PROCEDURE raise_salary (emp_id INTEGER, increase REAL) IS current_salary REAL;
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What are the types of Notation ?
Answer: Position, Named, Mixed and Restrictions.
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What all important parameters of the init.ora are supposed to be increased if you want to increase the SGA size ?
Answer: In our case, db_block_buffers was changed from 60 to 1000 (std values are 60, 550 & 3500) shared_pool_size was changed from 3.5MB to 9MB (std values are 3.5, 5 & 9MB) open_cursors was changed from 200 to 300 (std values are 200 & 300) db_block_size was changed from 2048 (2K) to 4096 (4K) {at the time of database creation}. The initial SGA was around 4MB when the server RAM was 32MB and The new SGA was around 13MB when the server RAM was increased to 128MB.
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If I have an execute privilege on a procedure in another users schema, can I execute his procedure even though I do not have privileges on the tables within the procedure ?
Answer: Yes
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What are various types of joins ?
Answer: Types of joins are:
Equijoins
Non-equijoins
self join
outer join
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What is a package cursor ?
Answer: A package cursor is a cursor which you declare in the package specification without an SQL statement.The SQL statement for the cursor is attached dynamically at runtime from calling procedures.
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If you insert a row in a table, then create another table and then say Rollback.In this case will the row be inserted ?
Answer: Yes.Because Create table is a DDL which commits automatically as soon as it is executed.The DDL commits the transaction even if the create statement fails internally (eg table already exists error) and not syntactically.

Oracle SQL/PLSQL Interview Questions with Answers


What are joins and Types of join?
Ans. We need retrive data from two or more tables to make our result complete. We need to perform a join.
INNER JOIN
This join returns rows when there is at least one match in both the tables.
OUTER JOIN
There are three different Outer Join methods.
LEFT OUTER JOIN
This join returns all the rows from the left table with the matching rows from the right table. If there are no field matching in the right table then it returns NULL values
RIGHT OUTER JOIN
Right outer join returns all the rows from the right table with the matching rows from the left table. If there are no field matching in the left table then it returns NULL values
FULL OUTER JOIN
Full outer join merge left outer join and right outer join.  this returns row from either table when the conditions are met and returns null value when there is no match
CROSS JOIN
Corss join is  does not necessary any condition to join. The output result contains records that are multiplication of record  from both the tables.

What is DIFFERENCE BETWEEN LEFT, RIGHT OUTER JOIN?
Ans:If there r any values in one table that do not have corresponding values in the other,in an equi join that row will not be selected.Such rows can be forcefully selected by using outer join symbol(+) on either of the sides(left or right)  based on the requirement.

WHAT ARE SET OPERATORS?
Ans: UNION, INTERSECT or MINUS is called SET OPERATORS.

What are different datatypes supported by sql in oracle?
Ans: Char (size), Nchar (size), Varchar2 (size), Nvarchar2 (size) data types for character values, Number (precision, scale), Number, Number (n), Float, Float (binary precision) data types for numerical values, Date data type for date values, Long, Raw (size),  Long Raw,  Clob, Blob, Nclob, Bfile for large objects.

What is difference between long and lob datatypes?
Ans:LOB
1) The maximum size is 4GB. 2) LOBs (except NCLOB) can be attributes of an object type. 3) LOBs support random access to data. 4) Multiple LOB columns per table or LOB attributes in an object type.
LONG
1) The maximum size is 2GB.  2) LONGs cannot.    3) LONGs support only sequential access. 4) Only one LONG column was allowed in a table

How much memory is allocated for date datatype? What is default date format in oracle?
Ans: For Date data type oracle allocates 7 bytes Memory.   Default Date Format is: DD-MON-YY.

What is range for each datatype of sql?
Ans: Datatype Range Char  Varchar2  Number    Float     LONG, RAW, LONGRAW  Large Objects (LOB’s) 2000 bytes  4000 bytes  Precision
1 to 38 Scale -84 to 127  Precision 38 decimals Or 122 binary precision   2 GB  4GB

What is a constraint? What are its various levels?
Ans: Constraint: Constraints are representators of the column to enforce data entity and consistency.There r two levels
1)Column-level constraints 2)Table-level constraints.

List out all the constraints supported by oracle
Primary Key , Foreign Key or Referential Integrity, Not Null, Unique, Check.

Difference between DELETE & TRUNCATE statement
Ans. Delete is a DML command. Truncate is a DDL command.
In Delete statement we can use where clause But we can’t use where clause in truncate statement.
Delete activates trigger. Truncate does not activate trigger.
We can rollback delete command. We can not rollback truncate command. Delete does not reset identity of table. Truncate resets identity of table.

 Difference between Primary key and Unique Key
Ans. Primary key and Unique key enforce uniqueness of the column on which they are defined. But by default, the primary key creates a clustered index on the column, where as unique key creates a non-clustered index by default. Another major difference is that primary key does not allow NULL value, but unique key allows one NULL value only.
 
What are  oracle number, character, date, conversion, other
functions.
Ans.
Oracle Number Functions –
Round (m, [n]),
Trunc (m, [n]),
Power (m, n),
Sqrt,
Abs (m),
Ceil (m),
Floor (m),
Mod (m, n)
  
Oracle Character Functions-
Chr (x)
Concert (string1, string2)
Lower (string)
Upper (string)
Substr (string, from_str, to_str)
ASCII (string)
Length (string)
Initcap (string). 
  
Oracle Date Functions-
sysdate
Months between (d1, d2)
To_char (d, format)
Last day (d)
Next_day (d, day).
Oracle Conversion Functions-
To_char
To_date
To_number

What is syntax of PL/SQL BLOCK
Ans. DECLARE
 <declarations>
 BEGIN
    <Exececutable Statements>
 EXCEPTION
    <Exception Handler(s)>
 END;
 
What are different types of oracle PL/SQL BLOCKS?
Ans:
Oracle PL/SQL DECLARE BLOCK – In DECLARE BLOCK all the declarations of the variable used in the program is made. If no variables are used this block will become optional.
Oracle PL/SQL BEGIN BLOCK -  In BEGIN BLOCK all the executable statements are placed. This block is Mandatory.
Oracle EXCEPTION BLOCK – In EXCEPTION BLOCK all the exceptions are handled. this block is optional.
 
 what is a Oracle PL/SQL cursor? and how to create cursor syntax?
Ans: Cursor is Private SQL area in PL/SQL.
     Declare the Cursor,
     Open the Cursor,
     Fetch values from SQL into the local Variables,
     Close the Cursor.
Type of cursors are supported by oracle pl/sql?
Ans.  There are two types of cursors namely Implicit Cursor, Explicit Cursor.

What is a cursor for loop?
Ans: Cursor For Loop is shortcut process for Explicit Cursors because the Cursor is Open, Rows are fetched once for each iteration and the cursor is closed automatically when all the rows have been processed.

What are cursor attributes?
Ans:  %Found, %NotFound,   %IsOpen, %RowCount are the cursor attributes.

 Use of cursor with “for update of” clause?
Ans: This Clause stop accessing of other users on the particular columns used by the cursor until the COMMIT is issued.

How Exception is different from error?
Ans: Whenever an error occurs Exception raises. Error is a bug whereas the Exception is a warning or error condition.

Oracle Backup and Recovery Interview Questions

Here are some interview questions and answers on Oracle Backup and Recovery. All of these interview questions and answers in real-time Oracle DBA interview questions and answers. Be careful with Oracle DBA interviews, as well as very strange SQL issues can be discussed during the interview. As a Oracle DBA candidate you can’t eliminate the real time scenario based backup and recovery interview questions during Oracle DBA interviews.


Q-1: One of my control file corrupted and I am unable start database, How can I perform recovery?

If one of your control file is missing or corrupted then we have 2 options to recover it. Check alert.log for exact name and location of corrupted control file. Delete it manually and copy from available rest of control file and rename it and start database. Another option is delete corrupted control file and remove name from parameter file/ spfile. After removing said control file from spfile, start your database.

Q-2: What is incremental checkpoint?

In incremental checkpoint process, CKPT process records lowest Low RBA to the control file to keep advancing the Buffer checkpoint Queue (BCQ) to make easy and fastest Active Checkpoint Queue (ACQ).

Q-3: Does incremental checkpoint recorded in Alert.log? How to disable it?

We can enable disable recording incremental checkpoint in alert.log .We can enable/disable recording using parameter log_checkpoints_to_alert=true/false.

Q-4: I am working as Oracle DBA in 24/7 running large production database. Size of database is around 800 GB. We take hot backup every day night. But one day at around 4:00 PM, by mistake one table is dropped by application user. Table is very useful. How to recover that dropped table?

If your database is running on Oracle 10g version then there is new feature available called Recyclebin. You can recover dropped table from user_recyclebin or dba_recyclebin.

Q-5: In continuation of above scenario, No. Recyclebin doesn’t enable in my database then how to I recover my table in above scenario?

Then you should need to restore backup on your UAT or test database server and enable time based recovery for applying all archives before drop command execution. For an instance, apply archives up to 3:55 PM here.

Q-6: In continuation of above scenario, why I should need to perform recovery in UAT or test database server? Can I restore backup in production database server?

No. It is not recommended because your production database is large database and running 24/7 environment. Restoration and recovery will take downtime. It is better to perform restoration and recovery process on UAT or Test database.

Q-7: What is the meaning of LGWR SYNC and LGWR ASYNC in log archive destination parameter for standby configuration?

When use LGWR with SYNC, it means once network I/O initiated, LGWR has to wait for completion of network I/O before write processing. LGWR with ASYNC, means LGWR doesn’t wait to finish network I/O and continuing write processing.

Q-8: How can I know my require table is available in export dump file or not?

Create indexfile of export dump file using import with indexfile command. A text file will be generating with all table and index object name with number of rows. You can confirm your require table object from this text file.

Q-9: Archive log are being generated around 20 GB in my production large database. But one day almost double archives were generated. What is the reason behind this? How can I check it?

There are lots of reason behind increasing size of archives like If more database changes were performed using batch jobs or any special task like merging 2 database or data etc. You can check it using enabling Log Minor utility.

Q-10: How do you recover from the loss of datafile if the DB is running in ARCHIVELOG mode?

We can perform this recovery in 2 ways. One is open database mode and another is database mount mode. After taking offline lost datafile, we can bring database open and after that restore lost datafile from last backup. After restoration of datafile we can perform datafile level recovery for applying archive logs and make it online. In database mount mode, we can restore datafile from backup and perform datafile recovery using “Recover datafile” command.

Q-11: What is a Complete Recovery?

During this recovery we are applying all database changes using archives log and make it to up to date. Complete recovery can be done full database level or datafile level or tablespace level. Main concept is to apply all data changes using archive logs and bring database up to recent time.

Q-12: Why we should need to open database using RESETLOGS after finishing incomplete recovery?

When we are performing incomplete recovery it means we bring database to past time or rewind period of time using change based, cancel based or time based recovery. These all recovery make database in prior state of database. The forward sequence number already available after performing recovery, due to mismatching of this sequence numbers and prior state of database, it needs to open database with new sequence number of Redo log and archive logs.

Q-13: Why export backup called as logical backup?

Export dump file doesn’t backup or contain any physical structure of database like datafile, control file, redo log file, parameter file, password file. Instead of physical structure, export dump contains logical structure of database like definition of tablespaces, segments, schemas, data of segments etc. Due to these reasons export dump is called as logical backup.

Q-14: Have you faced any recovery scenario? Explain us how you resolved it?

2 months back, a potential table was dropped by an application developer on our large 24/7 running production database. Immediately he informed us. We have standby database for our production database. We checked that archives didn’t apply to standby database up to dropped timing. We stopped archive applying on standby immediately and open database read only. Took export of dropped table and imported in production database. After finishing appropriate checking of table, again we started archive applying in standby database for refreshing.

Q-15: Which command I should need to execute to take backup of database which is running on NOARCHIVELOG mode?

Shutdown immediate. Because without shutdown, we can’t perform online backup of database, which running on NOARCHIVELOG mode. We should need to take cold backup of database.