Oracle Job Interview Questions Part-5

How do you trap the error in forms 3.0 ?
using On-Message or On-Error triggers.

How many pages you can in a single form ?
Unlimited

While specifying master/detail relationship between two blocks specifying the join condition is a must ?
True or False. ?
True

EXIT_FORM is a restricted package procedure ?
a. True b. False
True

What is the usage of an ON-INSERT,ON-DELETE and ON-UPDATE TRIGGERS ?
These triggers are executes when inserting, deleting and updating operations are performed and can be used to change the default function of insert, delete or update respectively. For Eg, instead of inserting a row in a table an existing row can be updated in the same table.

What are the types of Pop-up window ?
the pop-up field editor
pop-up list of values
pop-up pages.
Alert :

What is an SQL *FORMS ?
SQL *forms is 4GL tool for developing and executing; Oracle based interactive application.

How do you control the constraints in forms ?
Select the use constraint property is ON Block definition screen.
BLOCK

What is the difference between restricted and unrestricted package procedure ?
Restricted package procedure that affects the basic functions of SQL * Forms. It cannot used in all triggers except key triggers. Unrestricted package procedure that does not interfere with the basic functions of SQL * Forms it can be used in any triggers.

A query fetched 10 records How many times does a PRE-QUERY Trigger and POST-QUERY Trigger will get executed ?
PRE-QUERY fires once.
POST-QUERY fires 10 times.

Give the sequence in which triggers fired during insert operations, when the following 3 triggers are defined at the same block level ?
a. ON-INSERT b. POST-INSERT c. PRE-INSERT

State the order in which these triggers are executed ?
POST-FIELD,ON-VALIDATE-FIELD,POST-CHANGE and KEY-NEXTFLD. KEY-NEXTFLD,POST-CHANGE, ON-VALIDATE-FIELD, POST-FIELD. g.

What the PAUSE package procedure does ?
Pause suspends processing until the operator presses a function key

What do you mean by a page ?
Pages are collection of display information, such as constant text and graphics

What are the type of User Exits ?
ORACLE Precompliers user exits
OCI (ORACLE Call Interface)
Non-ORACEL user exits.
Page :

What is the difference between an ON-VALIDATE-FIELD trigger and a trigger ?
On-validate-field trigger fires, when the field Validation status New or changed. Post-field-trigger whenever the control leaving form the field, it will fire.

Can we use a restricted package procedure in ON-VALIDATE-FIELD Trigger ?
No

Is a Key startup trigger fires as result of a operator pressing a key explicitly ?
No

Can we use GO-BLOCK package in a pre-field trigger ?
No

Can we create two blocks with the same name in form 3.0 ?
No

What does an on-clear-block Trigger fire?
It fires just before SQL * forms the current block.

Name the two files that are created when you generate the form give the filex extension ?
INP (Source File)
FRM (Executable File)

What package procedure used for invoke sql *plus from sql *forms ?
Host (E.g. Host (sqlplus))

What is the significance of PAGE 0 in forms 3.0 ?
Hide the fields for internal calculation.

What are the different types of key triggers ?
Function Key
Key-function
Key-others
Key-startup

What is the difference between a Function Key Trigger and Key Function Trigger ?
Function key triggers are associated with individual SQL*FORMS function keys You can attach Key function triggers to 10 keys or key sequences that normally do not perform any SQL * FORMS operations. These keys referred as key F0 through key F9.

Committed block sometimes refer to a BASE TABLE ?
False

Error_Code is a package proecdure ?
a. True b. false
False

When is cost based optimization triggered? (for DBA)
It's important to have statistics on all tables for the CBO (Cost Based Optimizer) to work correctly. If one table involved in a statement does not have statistics, Oracle has to revert to rule-based optimization for that statement. So you really want for all tables to have statistics right away; it won't help much to just have the larger tables analyzed.
Generally, the CBO can change the execution plan when you:
1. Change statistics of objects by doing an ANALYZE;
2. Change some initialization parameters (for example: hash_join_enabled, sort_area_size, db_file_multiblock_read_count).

How can one optimize %XYZ% queries? (for DBA)
It is possible to improve %XYZ% queries by forcing the optimizer to scan all the entries from the index instead of the table. This can be done by specifying hints. If the index is physically smaller than the table (which is usually the case) it will take less time to scan the entire index than to scan the entire table.

What Enter package procedure does ?
Enter Validate-data in the current validation unit.

Where can one find I/O statistics per table? (for DBA)
The UTLESTAT report shows I/O per tablespace but one cannot see what tables in the tablespace has the most I/O. The $ORACLE_HOME/rdbms/admin/catio.sql script creates a sample_io procedure and table to gather the required information. After executing the procedure, one can do a simple SELECT * FROM io_per_object; to extract the required information. For more details, look at the header comments in the $ORACLE_HOME/rdbms/admin/catio.sql script.

My query was fine last week and now it is slow. Why? (for DBA)
The likely cause of this is because the execution plan has changed. Generate a current explain plan of the offending query and compare it to a previous one that was taken when the query was performing well. Usually the previous plan is not available.
Some factors that can cause a plan to change are:
. Which tables are currently analyzed? Were they previously analyzed? (ie. Was the query using RBO and now CBO?)
. Has OPTIMIZER_MODE been changed in INIT.ORA?
. Has the DEGREE of parallelism been defined/changed on any table?
. Have the tables been re-analyzed? Were the tables analyzed using estimate or compute? If estimate, what percentage was used?
. Have the statistics changed?
. Has the INIT.ORA parameter DB_FILE_MULTIBLOCK_READ_COUNT been changed?
. Has the INIT.ORA parameter SORT_AREA_SIZE been changed?
. Have any other INIT.ORA parameters been changed?
. What do you think the plan should be? Run the query with hints to see if this produces the required performance.

Why is Oracle not using the damn index? (for DBA)
This problem normally only arises when the query plan is being generated by the Cost Based Optimizer. The usual cause is because the CBO calculates that executing a Full Table Scan would be faster than accessing the table via the index.
Fundamental things that can be checked are:
. USER_TAB_COLUMNS.NUM_DISTINCT - This column defines the number of distinct values the column holds.
. USER_TABLES.NUM_ROWS - If NUM_DISTINCT = NUM_ROWS then using an index would be preferable to doing a FULL TABLE SCAN. As the NUM_DISTINCT decreases, the cost of using an index increase thereby is making the index less desirable.
. USER_INDEXES.CLUSTERING_FACTOR - This defines how ordered the rows are in the index. If CLUSTERING_FACTOR approaches the number of blocks in the table, the rows are ordered. If it approaches the number of rows in the table, the rows are randomly ordered. In such a case, it is unlikely that index entries in the same leaf block will point to rows in the same data blocks.
. Decrease the INIT.ORA parameter DB_FILE_MULTIBLOCK_READ_COUNT - A higher value will make the cost of a FULL TABLE SCAN cheaper.
. Remember that you MUST supply the leading column of an index, for the index to be used (unless you use a FAST FULL SCAN or SKIP SCANNING).
. There are many other factors that affect the cost, but sometimes the above can help to show why an index is not being used by the CBO. If from checking the above you still feel that the query should be using an index, try specifying an index hint. Obtain an explain plan of the query either using TKPROF with TIMED_STATISTICS, so that one can see the CPU utilization, or with AUTOTRACE to see the statistics. Compare this to the explain plan when not using an index.

When should one rebuild an index? (for DBA)
You can run the 'ANALYZE INDEX VALIDATE STRUCTURE' command on the affected indexes - each invocation of this command creates a single row in the INDEX_STATS view. This row is overwritten by the next ANALYZE INDEX command, so copy the contents of the view into a local table after each ANALYZE. The 'badness' of the index can then be judged by the ratio of 'DEL_LF_ROWS' to 'LF_ROWS'.

What are the unrestricted procedures used to change the popup screen position during run time ?
Anchor-view
Resize -View
Move-View.

What is an Alert ?
An alert is window that appears in the middle of the screen overlaying a portion of the current display.

Deleting a page removes information about all the fields in that page ?
a. True. b. False?
a. True.

Two popup pages can appear on the screen at a time ?Two popup pages can appear on the screen at a time ?
a. True. b. False?
a. True.

Classify the restricted and unrestricted procedure from the following.
a. Call
b. User-Exit
c. Call-Query
d. Up
e. Execute-Query
f. Message
g. Exit-From
h. Post
i. Break?

a. Call - unrestricted
b. User Exit - Unrestricted
c. Call_query - Unrestricted
d. Up - Restricted
e. Execute Query - Restricted
f. Message - Restricted
g. Exit_form - Restricted
h. Post - Restricted
i. Break - Unrestricted.

What is an User Exits ?
A user exit is a subroutine which are written in programming languages using pro*C pro *Cobol , etc., that link into the SQL * forms executable.

What is a Trigger ?
A piece of logic that is executed at or triggered by a SQL *forms event.

What is a Package Procedure ?
A Package procedure is built in PL/SQL procedure.

What is the maximum size of a form ?
255 character width and 255 characters Length.

What is the difference between system.current_field and system.cursor_field ?
1. System.current_field gives name of the field.
2. System.cursor_field gives name of the field with block name.

List the system variables related in Block and Field?
1. System.block_status
2. System.current_block
3. System.current_field
4. System.current_value
5. System.cursor_block
6. System.cursor_field
7. System.field_status.

What are the different types of Package Procedure ?
1. Restricted package procedure.
2. Unrestricted package procedure.

What are the types of TRIGGERS ?
1. Navigational Triggers.
2. Transaction Triggers.

Identify package function from the following ?
1. Error-Code
2. Break
3. Call
4. Error-text
5. Form-failure
6. Form-fatal
7. Execute-query
8. Anchor View
9. Message_code?

1. Error_Code
2. Error_Text
3. Form_Failure
4. Form_Fatal
5. Message_Code

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

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

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

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

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)

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.

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
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 execute the create_parameter_list built-in function to programmatically. 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.

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.

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

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

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

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

What built-in is used for changing the properties of the window dynamically?
Set_window_property
Canvas-View

What are the different types of windows?
Root window, secondary window.

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

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.

What are the different type of a record group?
Query record group
Static record group
Non query record group

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

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

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

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

Can you attach an alert to a field?
No

Can a root window be made modal?
No

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

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

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

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

What is the built-in routine used to count the no of rows in a group?
Get_group _row_count
System Variables

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

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.

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

List the built-in routine for controlling window 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
Alert

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

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

What buil-in routines are used to display editor dynamicaly?
Edit_text item
show_editor

Oracle Job Interview Questions Part-4

Where is the external query executed at the client or the server?
At the server.

Where is a procedure return in an external pl/sql library executed at the client or at the server?
At the client.

What is coordination Event?
Any event that makes a different record in the master block the current record is a coordination causing event.

What is the difference between OLE Server & Ole Container?
An Ole server application creates ole Objects that are embedded or linked in ole Containers ex. Ole servers are ms_word & ms_excel. OLE containers provide a place to store, display and manipulate objects that are created by ole server applications. Ex. oracle forms is an example of an ole Container.

What is an object group?
An object group is a container for a group of objects; you define an object group when you want to package related objects, so that you copy or reference them in other modules.

What is an LOV?
An LOV is a scrollable popup window that provides the operator with either a single or multi column selection list.

At what point of report execution is the before Report trigger fired?
After the query is executed but before the report is executed and the records are displayed.

What are the built -ins used for Modifying a groups structure?
ADD-GROUP_COLUMN (function)
ADD_GROUP_ROW (procedure)
DELETE_GROUP_ROW(procedure)

What is an user exit used for?
A way in which to pass control (and possibly arguments ) form Oracle report to another Oracle products of 3 GL and then return control ( and ) back to Oracle reports.

What is the User-Named Editor?
A user named editor has the same text editing functionality as the default editor, but, because it is a named object, you can specify editor attributes such as windows display size, position, and title.

My database was terminated while in BACKUP MODE, do I need to recover? (for DBA)
If a database was terminated while one of its tablespaces was in BACKUP MODE (ALTER TABLESPACE xyz BEGIN BACKUP;), it will tell you that media recovery is required when you try to restart the database. The DBA is then required to recover the database and apply all archived logs to the database. However, from Oracle7.2, you can simply take the individual datafiles out of backup mode and restart the database.
ALTER DATABASE DATAFILE '/path/filename' END BACKUP;
One can select from V$BACKUP to see which datafiles are in backup mode. This normally saves a significant amount of database down time.
Thiru Vadivelu contributed the following:
From Oracle9i onwards, the following command can be used to take all of the datafiles out of hot backup mode:
ALTER DATABASE END BACKUP;
The above commands need to be issued when the database is mounted.

What is a Static Record Group?
A static record group is not associated with a query, rather, you define its structure and row values at design time, and they remain fixed at runtime.

What is a record group?
A record group is an internal Oracle Forms that structure that has a column/row framework similar to a database table. However, unlike database tables, record groups are separate objects that belong to the form module which they are defined.

My database is down and I cannot restore. What now? (for DBA )
Recovery without any backup is normally not supported, however, Oracle Consulting can sometimes extract data from an offline database using a utility called DUL (Disk UnLoad). This utility reads data in the data files and unloads it into SQL*Loader or export dump files. DUL does not care about rollback segments, corrupted blocks, etc, and can thus not guarantee that the data is not logically corrupt. It is intended as an absolute last resort and will most likely cost your company a lot of money!!!

I've lost my REDOLOG files, how can I get my DB back? (for DBA)
The following INIT.ORA parameter may be required if your current redo logs are corrupted or blown away. Caution is advised when enabling this parameter as you might end-up losing your entire database. Please contact Oracle Support before using it. _allow_resetlogs_corruption = true

What is a property clause?
A property clause is a named object that contains a list of properties and their settings. Once you create a property clause you can base other object on it. An object based on a property can inherit the setting of any property in the clause that makes sense for that object.

What is a physical page ? & What is a logical page ?
A physical page is a size of a page. That is output by the printer. The logical page is the size of one page of the actual report as seen in the Previewer.

I've lost some Rollback Segments, how can I get my DB back? (for DBA)
Re-start your database with the following INIT.ORA parameter if one of your rollback segments is corrupted. You can then drop the corrupted rollback segments and create it from scratch.
Caution is advised when enabling this parameter, as uncommitted transactions will be marked as committed. One can very well end up with lost or inconsistent data!!! Please contact Oracle Support before using it. _Corrupted_rollback_segments = (rbs01, rbs01, rbs03, rbs04)

What are the differences between EBU and RMAN? (for DBA)
Enterprise Backup Utility (EBU) is a functionally rich, high performance interface for backing up Oracle7 databases. It is sometimes referred to as OEBU for Oracle Enterprise Backup Utility. The Oracle Recovery Manager (RMAN) utility that ships with Oracle8 and above is similar to Oracle7's EBU utility. However, there is no direct upgrade path from EBU to RMAN.

How does one create a RMAN recovery catalog? (for DBA)
Start by creating a database schema (usually called rman). Assign an appropriate tablespace to it and grant it the recovery_catalog_owner role. Look at this example:
sqlplus sys
SQL>create user rman identified by rman;
SQL> alter user rman default tablespace tools temporary tablespace temp;
SQL> alter user rman quota unlimited on tools;
SQL> grant connect, resource, recovery_catalog_owner to rman;
SQL> exit;
Next, log in to rman and create the catalog schema. Prior to Oracle 8i this was done by running the catrman.sql script. rman catalog rman/rman
RMAN>create catalog tablespace tools;
RMAN> exit;
You can now continue by registering your databases in the catalog. Look at this example:
rman catalog rman/rman target backdba/backdba
RMAN> register database;

How can a group in a cross products be visually distinguished from a group that does not form a cross product?
A group that forms part of a cross product will have a thicker border.

What is the frame & repeating frame?
A frame is a holder for a group of fields. A repeating frame is used to display a set of records when the no. of records that are to displayed is not known before.

What is a combo box?
A combo box style list item combines the features found in list and text item. Unlike the pop list or the text list style list items, the combo box style list item will both display fixed values and accept one operator entered value.

What are three panes that appear in the run time pl/sql interpreter?
1. Source pane.
2. interpreter pane.
3. Navigator pane.

What are the two panes that Appear in the design time pl/sql interpreter?
1. Source pane.
2. Interpreter pane

What are the two ways by which data can be generated for a parameters list of values?
1. Using static values.
2. Writing select statement.

What are the various methods of performing a calculation in a report ?
1. Perform the calculation in the SQL statements itself.
2. Use a calculated / summary column in the data model.

What are the default extensions of the files created by menu module?
.mmb,
.mmx

What are the default extensions of the files created by forms modules?
.fmb - form module binary
.fmx - form module executable

To display the page no. for each page on a report what would be the source & logical page no. or & of physical page no.?
& physical page no.

It is possible to use raw devices as data files and what is the advantages over file. system files ?
Yes. The advantages over file system files. I/O will be improved because Oracle is bye-passing the kernnel which writing into disk. Disk Corruption will be very less.

What are disadvantages of having raw devices ?
We should depend on export/import utility for backup/recovery (fully reliable) The tar command cannot be used for physical file backup, instead we can use dd command which is less flexible and has limited recoveries.

What is the significance of having storage clause ?
We can plan the storage for a table as how much initial extents are required, how much can be extended next, how much % should leave free for managing row updations etc.,

What is the use of INCTYPE option in EXP command ?
Type export should be performed COMPLETE,CUMULATIVE,INCREMENTAL. List the sequence of events when a large transaction that exceeds beyond its optimal value when an entry wraps and causes the rollback segment toexpand into anotion Completes. e. will be written.

What is the use of FILE option in IMP command ?
The name of the file from which import should be performed.

What is a Shared SQL pool?
The data dictionary cache is stored in an area in SGA called the Shared SQL Pool. This will allow sharing of parsed SQL statements among concurrent users.

What is hot backup and how it can be taken?
Taking backup of archive log files when database is open. For this the ARCHIVELOG mode should be enabled. The following files need to be backed up. All data files. All Archive log, redo log files. All control files.

List the Optional Flexible Architecture (OFA) of Oracle database? or How can we organize the tablespaces in Oracle database to have maximum performance ?
SYSTEM - Data dictionary tables.
DATA - Standard operational tables.
DATA2- Static tables used for standard operations
INDEXES - Indexes for Standard operational tables.
INDEXES1 - Indexes of static tables used for standard operations.
TOOLS - Tools table.
TOOLS1 - Indexes for tools table.
RBS - Standard Operations Rollback Segments,
RBS1,RBS2 - Additional/Special Rollback segments.
TEMP - Temporary purpose tablespace
TEMP_USER - Temporary tablespace for users.
USERS - User tablespace.

How to implement the multiple control files for an existing database ?
Shutdown the database Copy one of the existing control file to new location Edit Config ora file by adding new control file. name Restart the database.

What is advantage of having disk shadowing/ Mirroring ?
Shadow set of disks save as a backup in the event of disk failure. In most Operating System if any disk failure occurs it automatically switchover to place of failed disk. Improved performance because most OS support volume shadowing can direct file I/O request to use the shadow set of files instead of the main set of files. This reduces I/O load on the main set of disks.

How will you force database to use particular rollback segment ?
SET TRANSACTION USE ROLLBACK SEGMENT rbs_name.

Why query fails sometimes ?
Rollback segment dynamically extent to handle larger transactions entry loads. A single transaction may wipeout all available free space in the Rollback Segment Tablespace. This prevents other user using Rollback segments.

What is the use of RECORD LENGTH option in EXP command ?
Record length in bytes.

How will you monitor rollback segment status ?
Querying the DBA_ROLLBACK_SEGS view
IN USE - Rollback Segment is on-line.
AVAILABLE - Rollback Segment available but not on-line.
OFF-LINE - Rollback Segment off-line
INVALID - Rollback Segment Dropped.
NEEDS RECOVERY - Contains data but need recovery or corupted.
PARTLY AVAILABLE - Contains data from an unresolved transaction involving a distributed database.

What is meant by Redo Log file mirroring ? How it can be achieved?
Process of having a copy of redo log files is called mirroring. This can be achieved by creating group of log files together, so that LGWR will automatically writes them to all the members of the current on-line redo log group. If any one group fails then database automatically switch over to next group. It degrades performance.

Which parameter in Storage clause will reduce no. of rows per block?
PCTFREE parameter
Row size also reduces no of rows per block.

What is meant by recursive hints ?
Number of times processes repeatedly query the dictionary table is called recursive hints. It is due to the data dictionary cache is too small. By increasing the SHARED_POOL_SIZE parameter we can optimize the size of Data Dictionary Cache.

What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.

What is the difference between locks, latches, enqueues and semaphores? (for DBA)
A latch is an internal Oracle mechanism used to protect data structures in the SGA from simultaneous access. Atomic hardware instructions like TEST-AND-SET is used to implement latches. Latches are more restrictive than locks in that they are always exclusive. Latches are never queued, but will spin or sleep until they obtain a resource, or time out.
Enqueues and locks are different names for the same thing. Both support queuing and concurrency. They are queued and serviced in a first-in-first-out (FIFO) order.
Semaphores are an operating system facility used to control waiting. Semaphores are controlled by the following Unix parameters: semmni, semmns and semmsl. Typical settings are:
semmns = sum of the "processes" parameter for each instance
(see init.ora for each instance)
semmni = number of instances running simultaneously;
semmsl = semmns

What is a logical backup?
Logical backup involves reading a set of database records and writing them into a file. Export utility is used for taking backup and Import utility is used to recover from backup.

Where can one get a list of all hidden Oracle parameters? (for DBA)
Oracle initialization or INIT.ORA parameters with an underscore in front are hidden or unsupported parameters. One can get a list of all hidden parameters by executing this query:
select *
from SYS.X$KSPPI
where substr(KSPPINM,1,1) = '_';
The following query displays parameter names with their current value:
select a.ksppinm "Parameter", b.ksppstvl "Session Value", c.ksppstvl "Instance Value"
from x$ksppi a, x$ksppcv b, x$ksppsv c
where a.indx = b.indx and a.indx = c.indx
and substr(ksppinm,1,1)='_'
order by a.ksppinm;
Remember: Thou shall not play with undocumented parameters!

What is a database EVENT and how does one set it? (for DBA)
Oracle trace events are useful for debugging the Oracle database server. The following two examples are simply to demonstrate syntax. Refer to later notes on this page for an explanation of what these particular events do.
Either adding them to the INIT.ORA parameter file can activate events. E.g.
event='1401 trace name errorstack, level 12'
... or, by issuing an ALTER SESSION SET EVENTS command: E.g.
alter session set events '10046 trace name context forever, level 4';
The alter session method only affects the user's current session, whereas changes to the INIT.ORA file will affect all sessions once the database has been restarted.

What is a Rollback segment entry ?
It is the set of before image data blocks that contain rows that are modified by a transaction. Each Rollback Segment entry must be completed within one rollback segment. A single rollback segment can have multiple rollback segment entries.

What database events can be set? (for DBA)
The following events are frequently used by DBAs and Oracle Support to diagnose problems:
" 10046 trace name context forever, level 4 Trace SQL statements and show bind variables in trace output.
" 10046 trace name context forever, level 8 This shows wait events in the SQL trace files
" 10046 trace name context forever, level 12 This shows both bind variable names and wait events in the SQL trace files
" 1401 trace name errorstack, level 12 1401 trace name errorstack, level 4 1401 trace name processstate Dumps out trace information if an ORA-1401 "inserted value too large for column" error occurs. The 1401 can be replaced by any other Oracle Server error code that you want to trace.
" 60 trace name errorstack level 10 Show where in the code Oracle gets a deadlock (ORA-60), and may help to diagnose the problem.
The following lists of events are examples only. They might be version specific, so please call Oracle before using them:
" 10210 trace name context forever, level 10 10211 trace name context forever, level 10 10231 trace name context forever, level 10 These events prevent database block corruptions
" 10049 trace name context forever, level 2 Memory protect cursor
" 10210 trace name context forever, level 2 Data block check
" 10211 trace name context forever, level 2 Index block check
" 10235 trace name context forever, level 1 Memory heap check
" 10262 trace name context forever, level 300 Allow 300 bytes memory leak for connections
Note: You can use the Unix oerr command to get the description of an event. On Unix, you can type "oerr ora 10053" from the command prompt to get event details.

How can one dump internal database structures? (for DBA)
The following (mostly undocumented) commands can be used to obtain information about internal database structures.
o Dump control file contents
alter session set events 'immediate trace name CONTROLF level 10'
/
o Dump file headers
alter session set events 'immediate trace name FILE_HDRS level 10'
/
o Dump redo log headers
alter session set events 'immediate trace name REDOHDR level 10'
/
o Dump the system state
NOTE: Take 3 successive SYSTEMSTATE dumps, with 10-minute intervals alter session set events 'immediate trace name SYSTEMSTATE level 10'
/
o Dump the process state
alter session set events 'immediate trace name PROCESSSTATE level 10'
/
o Dump Library Cache details
alter session set events 'immediate trace name library cache level 10'
/
o Dump optimizer statistics whenever a SQL statement is parsed (hint: change statement or flush pool) alter session set events '10053 trace name context forever, level 1'
/
o Dump a database block (File/ Block must be converted to DBA address) Convert file and block number to a DBA (database block address).
Eg: variable x varchar2;
exec :x := dbms_utility.make_data_block_address(1,12);
print x
alter session set events 'immediate trace name blockdump level 50360894'
/

What are the different kind of export backups?
Full back - Complete database
Incremental - Only affected tables from last incremental date/full backup date.
Cumulative backup - Only affected table from the last cumulative date/full backup date.

How free extents are managed in Ver 6.0 and Ver 7.0 ?
Free extents cannot be merged together in Ver 6.0.
Free extents are periodically coalesces with the neighboring free extent in Ver 7.0

What is the use of RECORD option in EXP command?
For Incremental exports, the flag indirects whether a record will be stores data dictionary tables recording the export.

What is the use of ROWS option in EXP command ?
Flag to indicate whether table rows should be exported. If 'N' only DDL statements for the database objects will be created.

What is the use of COMPRESS option in EXP command ?
Flag to indicate whether export should compress fragmented segments into single extents.

How will you swap objects into a different table space for an existing database ?
Export the user
Perform import using the command imp system/manager file=export.dmp indexfile=newrite.sql.
This will create all definitions into newfile.sql. Drop necessary objects.
Run the script newfile.sql after altering the tablespaces.
Import from the backup for the necessary objects.

How does Space allocation table place within a block ?
Each block contains entries as follows
Fixed block header
Variable block header
Row Header,row date (multiple rows may exists)
PCTEREE (% of free space for row updation in future)

What are the factors causing the reparsing of SQL statements in SGA?
Due to insufficient Shared SQL pool size. Monitor the ratio of the reloads takes place while executing SQL statements. If the ratio is greater than 1 then increase the SHARED_POOL_SIZE. LOGICAL & PHYSICAL ARCHITECTURE OF DATABASE.

What is dictionary cache ?
Dictionary cache is information about the databse objects stored in a data dictionary table.

What is a Control file ?
Database overall physical architecture is maintained in a file called control file. It will be used to maintain internal consistency and guide recovery operations. Multiple copies of control files are advisable.

What is Database Buffers ?
Database buffers are cache in the SGA used to hold the data blocks that are read from the data segments in the database such as tables, indexes and clusters DB_BLOCK_BUFFERS parameter in INIT.ORA decides the size.

How will you create multiple rollback segments in a database ?
Create a database which implicitly creates a SYSTEM Rollback Segment in a SYSTEM tablespace. Create a Second Rollback Segment name R0 in the SYSTEM tablespace. Make new rollback segment available (After shutdown, modify init.ora file and Start database) Create other tablespaces (RBS) for rollback segments. Deactivate Rollback Segment R0 and activate the newly created rollback segments.

What is cold backup? What are the elements of it?
Cold backup is taking backup of all physical files after normal shutdown of database. We need to take.
- All Data files.
- All Control files.
- All on-line redo log files.
- The init.ora file (Optional)

What is meant by redo log buffer ?
Changes made to entries are written to the on-line redo log files. So that they can be used in roll forward operations during database recoveries. Before writing them into the redo log files, they will first brought to redo log buffers in SGA and LGWR will write into files frequently. LOG_BUFFER parameter will decide the size.

How will you estimate the space required by a non-clustered tables?
Calculate the total header size
Calculate the available dataspace per data block
Calculate the combined column lengths of the average row
Calculate the total average row size.
Calculate the average number rows that can fit in a block
Calculate the number of blocks and bytes required for the table.
After arriving the calculation, add 10 % additional space to calculate the initial extent size for a working table.

How will you monitor the space allocation ?
By querying DBA_SEGMENT table/view.

What is meant by free extent ?
A free extent is a collection of continuous free blocks in tablespace. When a segment is dropped its extents are reallocated and are marked as free.

What is the use of IGNORE option in IMP command ?
A flag to indicate whether the import should ignore errors encounter when issuing CREATE commands.

What is the use of ANALYSE ( Ver 7) option in EXP command ?
A flag to indicate whether statistical information about the exported objects should be written to export dump file.

What is the use of ROWS option in IMP command ?
A flag to indicate whether rows should be imported. If this is set to 'N' then only DDL for database objects will be executed.

What is the use of INDEXES option in EXP command ?
A flag to indicate whether indexes on tables will be exported.

What is the use of INDEXES option in IMP command ?
A flag to indicate whether import should import index on tables or not.

What is the use of GRANT option in EXP command?
A flag to indicate whether grants on databse objects will be exported or not. Value is 'Y' or 'N'.

What is the use of GRANT option in IMP command ?
A flag to indicate whether grants on database objects will be imported.

What is the use of FULL option in EXP command ?
A flag to indicate whether full databse export should be performed.

What is the use of SHOW option in IMP command ?
A flag to indicate whether file content should be displayed or not.

What is the use of CONSTRAINTS option in EXP command ?
A flag to indicate whether constraints on table need to be exported.

What is the use of CONSISTENT (Ver 7) option in EXP command ?
A flag to indicate whether a read consistent version of all the exported objects should be maintained.

What are the different methods of backing up oracle database ?
- Logical Backups
- Cold Backups
- Hot Backups (Archive log)

What is the difference between ON-VALIDATE-FIELD trigger and a POST-CHANGE trigger ?
When you changes the Existing value to null, the On-validate field trigger will fire post change trigger will not fire. At the time of execute-query post-change trigger will fire, on-validate field trigger will not fire.

When is PRE-QUERY trigger executed ?
When Execute-query or count-query Package procedures are invoked.