ORACLE PAPER - 30 NOV 2008
1. Is it possible to split the print reviewer into more than one region?
2. Is it possible to center an object horizontally in a repeating frame that has a variable horizontal size?
3. For a field in a repeating frame, can the source come from the column which does not exist in the data group which forms the base for the frame?
4. Can a field be used in a report without it appearing in any data group?
5. The join defined by the default data link is an outer join yes or no?
6. Can a formula column referred to columns in higher group?
7. Can a formula column be obtained through a select statement?
8. Is it possible to insert comments into sql statements return in the data model editor?
9. Is it possible to disable the parameter from while running the report?
10. When a form is invoked with call_form, Does oracle forms issues a save point?
11. Explain the difference between a hot backup and a cold backup and the benefits associated with each.
A hot backup is basically taking a backup of the database while it is still up and running and it must be in archive log mode. A cold backup is taking a backup of the database while it is shut down and does not require being in archive log mode. The benefit of taking a hot backup is that the database is still available for use while the backup is occurring and you can recover the database to any point in time. The benefit of taking a cold backup is that it is typically easier to administer the backup and recovery process. In addition, since you are taking cold backups the database does not require being in archive log mode and thus there will be a slight performance gain as the database is not cutting archive logs to disk.
12. You have just had to restore from backup and do not have any control files. How would you go about bringing up this database?
I would create a text based backup control file, stipulating where on disk all the data files where and then issue the recover command with the using backup control file clause.
13. How do you switch from an init.ora file to a spfile?
Issue the create spfile from pfile command.
14. Explain the difference between a data block, an extent and a segment.
A data block is the smallest unit of logical storage for a database object. As objects grow they take chunks of additional storage that are composed of contiguous data blocks. These groupings of contiguous data blocks are called extents. All the extents that an object takes when grouped together are considered the segment of the database object.
15. Give two examples of how you might determine the structure of the table DEPT.
Use the describe command or use the dbms_metadata.get_ddl package.
16. Where would you look for errors from the database engine?
In the alert log.
17. Compare and contrast TRUNCATE and DELETE for a table.
Both the truncate and delete command have the desired outcome of getting rid of all the rows in a table. The difference between the two is that the truncate command is a DDL operation and just moves the high water mark and produces a now rollback. The delete command, on the other hand, is a DML operation, which will produce a rollback and thus take longer to complete.
18. Give the reasoning behind using an index.
Faster access to data blocks in a table.
19. Give the two types of tables involved in producing a star schema and the type of data they hold.
Fact tables and dimension tables. A fact table contains measurements while dimension tables will contain data that will help describe the fact tables.
20. What type of index should you use on a fact table?
A Bitmap index.
21. Give two examples of referential integrity constraints.
A primary key and a foreign key.
22. A table is classified as a parent table and you want to drop and re-create it. How would you do this without affecting the children tables?
Disable the foreign key constraint to the parent, drop the table, re-create the table, enable the foreign key constraint.
23. Explain the difference between ARCHIVELOG mode and NOARCHIVELOG mode and the benefits and disadvantages to each.
ARCHIVELOG mode is a mode that you can put the database in for creating a backup of all transactions that have occurred in the database so that you can recover to any point in time. NOARCHIVELOG mode is basically the absence of ARCHIVELOG mode and has the disadvantage of not being able to recover to any point in time. NOARCHIVELOG mode does have the advantage of not having to write transactions to an archive log and thus increases the performance of the database slightly.
24. What command would you use to create a backup control file?
Alter database backup control file to trace.
25. Give the stages of instance startup to a usable state where normal users may access it.
STARTUP NOMOUNT - Instance startup
STARTUP MOUNT - The database is mounted
STARTUP OPEN - The database is opened
26. What column differentiates the V$ views to the GV$ views and how?
The INST_ID column which indicates the instance in a RAC environment the information came from.
27. How would you go about generating an EXPLAIN plan?
Create a plan table with utlxplan.sql.
Use the explain plan set statement_id = 'tst1' into plan_table for a SQL statement
Look at the explain plan with utlxplp.sql or utlxpls.sql
28. How would you go about increasing the buffer cache hit ratio?
Use the buffer cache advisory over a given workload and then query the v$db_cache_advice table. If a change was necessary then I would use the alter system set db_cache_size command.
29. Explain an ORA-01555
You get this error when you get a snapshot too old within rollback. It can usually be solved by increasing the undo retention or increasing the size of rollbacks. You should also look at the logic involved in the application getting the error message.
30. Explain the difference between $ORACLE_HOME and $ORACLE_BASE.
ORACLE_BASE is the root directory for oracle. ORACLE_HOME located beneath ORACLE_BASE is where the oracle products reside.
31. How would you determine the time zone under which a database was operating?
select DBTIMEZONE from dual;
32. Explain the use of setting GLOBAL_NAMES equal to TRUE.
Setting GLOBAL_NAMES dictates how you might connect to a database. This variable is either TRUE or FALSE and if it is set to TRUE it enforces database links to have the same name as the remote database to which they are linking.
33. What command would you use to encrypt a PL/SQL application?
34. Explain the difference between a FUNCTION, PROCEDURE and PACKAGE.
A function and procedure are the same in that they are intended to be a collection of PL/SQL code that carries a single task. While a procedure does not have to return any values to the calling application, a function will return a single value. A package on the other hand is a collection of functions and procedures that are grouped together based on their commonality to a business function or application.
35. Explain the use of table functions.
Table functions are designed to return a set of rows through PL/SQL logic but are intended to be used as a normal table or view in a SQL statement. They are also used to pipeline information in an ETL process.
36. Name three advisory statistics you can collect.
Buffer Cache Advice, Segment Level Statistics, & Timed Statistics
37. Where in the Oracle directory tree structure are audit traces placed?
In unix $ORACLE_HOME/rdbms/audit, in Windows the event viewer
38. Explain materialized views and how they are used.
Materialized views are objects that are reduced sets of information that have been summarized, grouped, or aggregated from base tables. They are typically used in data warehouse or decision support systems.
39. When a user process fails, what background process cleans up after it?
40. What background process refreshes materialized views?
The Job Queue Processes.
41. How would you determine what sessions are connected and what resources they are waiting for?
Use of V$SESSION and V$SESSION_WAIT
42. Describe what redo logs are.
Redo logs are logical and physical structures that are designed to hold all the changes made to a database and are intended to aid in the recovery of a database.
43. How would you force a log switch?
ALTER SYSTEM SWITCH LOGFILE;
44. Give two methods you could use to determine what DDL changes have been made.
You could use Logminer or Streams
45. What does coalescing a tablespace do?
Coalescing is only valid for dictionary-managed tablespaces and de-fragments space by combining neighboring free extents into large single extents.
46. What is the difference between a TEMPORARY tablespace and a PERMANENT tablespace?
A temporary tablespace is used for temporary objects such as sort structures while permanent tablespaces are used to store those objects meant to be used as the true objects of the database.
47. Name a tablespace automatically created when you create a database.
The SYSTEM tablespace.
48. When creating a user, what permissions must you grant to allow them to connect to the database?
Grant the CONNECT to the user
49. How do you add a data file to a tablespace
ALTER TABLESPACE <tablespace_name> ADD DATAFILE <datafile_name> SIZE
50. How do you resize a data file?
ALTER DATABASE DATAFILE <datafile_name> RESIZE <new_size>;
51. What view would you use to look at the size of a data file?
52. What view would you use to determine free space in a tablespace?
53. How would you determine who has added a row to a table?
Turn on fine grain auditing for the table.
54. How can you rebuild an index?
ALTER INDEX <index_name> REBUILD;
55. Explain what partitioning is and what its benefit is.
Partitioning is a method of taking large tables and indexes and splitting them into smaller, more manageable pieces.
56. You have just compiled a PL/SQL package but got errors, how would you view the errors?
57. How can you gather statistics on a table?
The ANALYZE command.
58. How can you enable a trace for a session?
Use the DBMS_SESSION.SET_SQL_TRACE or
Use ALTER SESSION SET SQL_TRACE = TRUE;
59. What is the difference between the SQL*Loader and IMPORT utilities?
These two Oracle utilities are used for loading data into the database. The difference is that the import utility relies on the data being produced by another Oracle utility EXPORT while the SQL*Loader utility allows data to be loaded that has been produced by other utilities from different data sources just so long as it conforms to ASCII formatted or delimited files.
60. Name two files used for network connection to a database.
TNSNAMES.ORA and SQLNET.ORA
61. What is the function of Optimizer ?
The goal of the optimizer is to choose the most efficient way to execute a SQL statement.
62. What is Execution Plan ?
The combinations of the steps the optimizer chooses to execute a statement is called an execution plan.
63. Can one resize tablespaces and data files? (for DBA)
One can manually increase or decrease the size of a datafile from Oracle 7.2 using the command.
ALTER DATABASE DATAFILE 'filename2' RESIZE 100M;
Because you can change the sizes of datafiles, you can add more space to your database without adding more datafiles. This is beneficial if you are concerned about reaching the maximum number of datafiles allowed in your database.
Manually reducing the sizes of datafiles allows you to reclaim unused space in the database. This is useful for correcting errors in estimations of space requirements.
Also, datafiles can be allowed to automatically extend if more space is required. Look at the following command:
CREATE TABLESPACE pcs_data_ts
DATAFILE 'c:ora_appspcspcsdata1.dbf' SIZE 3M
AUTOEXTEND ON NEXT 1M MAXSIZE UNLIMITED
DEFAULT STORAGE (INITIAL 10240
64. What is SAVE POINT ?
For long transactions that contain many SQL statements, intermediate markers or savepoints can be declared which can be used to divide a transaction into smaller parts. This allows the option of later rolling back all work performed from the current point in the transaction to a declared savepoint within the transaction.
65. What are the values that can be specified for OPTIMIZER MODE Parameter ?
COST and RULE.
66. Can one rename a tablespace? (for DBA)
No, this is listed as Enhancement Request 148742. Workaround:
Export all of the objects from the tablespace
Drop the tablespace including contents
Recreate the tablespace
Import the objects
67. What is RULE-based approach to optimization ?
Choosing an executing planbased on the access paths available and the ranks of these access paths.
68. What are the values that can be specified for OPTIMIZER_GOAL parameter of the ALTER SESSION Command ? )
CHOOSE, ALL_ROWS, FIRST_ROWS and RULE.
69. How does one create a standby database? (for DBA)
While your production database is running, take an (image copy) backup and restore it on duplicate hardware. Note that an export will not work!!!
On your standby database, issue the following commands:
ALTER DATABASE CREATE STANDBY CONTROLFILE AS 'filename';
ALTER DATABASE MOUNT STANDBY DATABASE;
RECOVER STANDBY DATABASE;
On systems prior to Oracle 8i, write a job to copy archived redo log files from the primary database to the standby system, and apply the redo log files to the standby database (pipe it). Remember the database is recovering and will prompt you for the next log file to apply.
Oracle 8i onwards provide an "Automated Standby Database" feature, which will send archived, log files to the remote site via NET8, and apply then to the standby database.
When one needs to activate the standby database, stop the recovery process and activate it:
70. How does one give developers access to trace files (required as input to tkprof)? (for DBA)
The "alter session set sql_trace=true" command generates trace files in USER_DUMP_DEST that can be used by developers as input to tkprof. On Unix the default file mask for these files are "rwx r-- ---".
There is an undocumented INIT.ORA parameter that will allow everyone to read (rwx r-r--) these trace files:
_trace_files_public = true
Include this in your INIT.ORA file and bounce your database for it to take effect.
71. What are the responsibilities of a Database Administrator ?
Installing and upgrading the Oracle Server and application tools. Allocating system storage and planning future storage requirements for the database system. Managing primary database structures (tablespaces) Managing primary objects (table,views,indexes) Enrolling users and maintaining system security. Ensuring compliance with Oralce license agreement Controlling and monitoring user access to the database. Monitoring and optimizing the performance of the database. Planning for backup and recovery of database information. Maintain archived data on tape Backing up and restoring the database. Contacting Oracle Corporation for technical support.
72. What is a trace file and how is it created ?
Each server and background process can write an associated trace file. When an internal error is detected by a process or user process, it dumps information about the error to its trace. This can be used for tuning the database.
73. What are the roles and user accounts created automatically with the database?
DBA - role Contains all database system privileges.
SYS user account - The DBA role will be assigned to this account. All of the base tables and views for the database's dictionary are store in this schema and are manipulated only by ORACLE.
SYSTEM user account - It has all the system privileges for the database and additional tables and views that display administrative information and internal tables and views used by oracle tools are created using this username.
74. What are the minimum parameters should exist in the parameter file (init.ora) ?
DB NAME - Must set to a text string of no more than 8 characters and it will be stored inside the datafiles, redo log files and control files and control file while database creation.
DB_DOMAIN - It is string that specifies the network domain where the database is created. The global database name is identified by setting these parameters
(DB_NAME & DB_DOMAIN) CONTORL FILES - List of control filenames of the database. If name is not mentioned then default name will be used.
DB_BLOCK_BUFFERS - To determine the no of buffers in the buffer cache in SGA.
PROCESSES - To determine number of operating system processes that can be connected to ORACLE concurrently. The value should be 5 (background process) and additional 1 for each user.
ROLLBACK_SEGMENTS - List of rollback segments an ORACLE instance acquires at database startup. Also optionally LICENSE_MAX_SESSIONS,LICENSE_SESSION_WARNING and LICENSE_MAX_USERS.
75. Why and when should I backup my database? (for DBA)
Backup and recovery is one of the most important aspects of a DBAs job. If you lose your company's data, you could very well lose your job. Hardware and software can always be replaced, but your data may be irreplaceable!
Normally one would schedule a hierarchy of daily, weekly and monthly backups, however consult with your users before deciding on a backup schedule. Backup frequency normally depends on the following factors:
. Rate of data change/ transaction rate
. Database availability/ Can you shutdown for cold backups?
. Criticality of the data/ Value of the data to the company
. Read-only tablespace needs backing up just once right after you make it read-only
. If you are running in archivelog mode you can backup parts of a database over an extended cycle of days
. If archive logging is enabled one needs to backup archived log files timeously to prevent database freezes
Carefully plan backup retention periods. Ensure enough backup media (tapes) are available and that old backups are expired in-time to make media available for new backups. Off-site vaulting is also highly recommended.
Frequently test your ability to recover and document all possible scenarios. Remember, it's the little things that will get you. Most failed recoveries are a result of organizational errors and miscommunications.
76. What strategies are available for backing-up an Oracle database? (for DBA
The following methods are valid for backing-up an Oracle database:
Export/Import - Exports are "logical" database backups in that they extract logical definitions and data from the database to a file.
Cold or Off-line Backups - Shut the database down and backup up ALL data, log, and control files.
Hot or On-line Backups - If the databases are available and in ARCHIVELOG mode, set the tablespaces into backup mode and backup their files. Also remember to backup the control files and archived redo log files.
RMAN Backups - While the database is off-line or on-line, use the "rman" utility to backup the database.
It is advisable to use more than one of these methods to backup your database. For example, if you choose to do on-line database backups, also cover yourself by doing database exports. Also test ALL backup and recovery scenarios carefully. It is better to be save than sorry.
Regardless of your strategy, also remember to backup all required software libraries, parameter files, password files, etc. If your database is in ARCGIVELOG mode, you also need to backup archived log files.
77. What is the difference between online and offline backups? (for DBA
A hot backup is a backup performed while the database is online and available for read/write. Except for Oracle exports, one can only do on-line backups when running in ARCHIVELOG mode.
A cold backup is a backup performed while the database is off-line and unavailable to its users.
78. What is the difference between restoring and recovering? (for DBA
Restoring involves copying backup files from secondary storage (backup media) to disk. This can be done to replace damaged files or to copy/move a database to a new location.
Recovery is the process of applying redo logs to the database to roll it forward. One can roll-forward until a specific point-in-time (before the disaster occurred), or roll-forward until the last transaction recorded in the log files. Sql> connect SYS as SYSDBA
Sql> RECOVER DATABASE UNTIL TIME '2001-03-06:16:00:00' USING BACKUP CONTROLFILE;
79. How does one backup a database using the export utility? (for DBA
Oracle exports are "logical" database backups (not physical) as they extract data and logical definitions from the database into a file. Other backup strategies normally back-up the physical data files.
One of the advantages of exports is that one can selectively re-import tables, however one cannot roll-forward from an restored export file. To completely restore a database from an export file one practically needs to recreate the entire database.
Always do full system level exports (FULL=YES). Full exports include more information about the database in the export file than user level exports.
80. What are the built_ins used the display the LOV?
81. How do you call other Oracle Products from Oracle Forms?
Run_product is a built-in, Used to invoke one of the supported oracle tools products and specifies the name of the document or module to be run. If the called product is unavailable at the time of the call, Oracle Forms returns a message to the operator.
82. What are the Built-ins to display the user-named editor?
A user named editor can be displayed programmatically with the built in procedure SHOW-EDITOR, EDIT_TETITEM independent of any particular text item.
83. How many number of columns a record group can have?
A record group can have an unlimited number of columns of type CHAR, LONG, NUMBER, or DATE provided that the total number of column does not exceed 64K.
84. What is a Query Record Group?
A query record group is a record group that has an associated SELECT statement. The columns in a query record group derive their default names, data types, had lengths from the database columns referenced in the SELECT statement. The records in query record group are the rows retrieved by the query associated with that record group. What is a Non Query Record Group?
85. What does the term panel refer to with regard to pages?
A panel is the no. of physical pages needed to print one logical page.
86. What is a master detail relationship?
A master detail relationship is an association between two base table blocks- a master block and a detail block. The relationship between the blocks reflects a primary key to foreign key relationship between the tables on which the blocks are based.
87.What is a library?
A library is a collection of subprograms including user named procedures, functions and packages.
88. What is an anchoring object and what is its use? What are the various sub events a mouse double click event involves?
An anchoring object is a print condition object which used to explicitly or implicitly anchor other objects to itself.
89. Use the add_group_column function to add a column to record group that was created at a design time?
90. 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.
91. What is the use of break group? What are the various sub events a mouse double click event involves?
A break group is used to display one record for one group ones. While multiple related records in other group can be displayed.
92. What tuning indicators can one use? (for DBA
The following high-level tuning indicators can be used to establish if a database is performing optimally or not:
. Buffer Cache Hit Ratio
Formula: Hit Ratio = (Logical Reads - Physical Reads) / Logical Reads
Action: Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i) to increase hit ratio
. Library Cache Hit Ratio
Action: Increase the SHARED_POOL_SIZE to increase hit ratio
93. What tools/utilities does Oracle provide to assist with performance tuning? (for DBA
Oracle provide the following tools/ utilities to assist with performance monitoring and tuning:
. UTLBSTAT.SQL and UTLESTAT.SQL - Begin and end stats monitoring
. Oracle Enterprise Manager - Tuning Pack
94. What is STATSPACK and how does one use it? (for DBA
Statspack is a set of performance monitoring and reporting utilities provided by Oracle from Oracle8i and above. Statspack provides improved BSTAT/ESTAT functionality, though the old BSTAT/ESTAT scripts are still available. For more information about STATSPACK, read the documentation in file $ORACLE_HOME/rdbms/admin/spdoc.txt.
sqlplus "/ as sysdba" @spdrop.sql -- Install Statspack -
sqlplus "/ as sysdba" @spcreate.sql-- Enter tablespace names when prompted
exec statspack.snap; -- Take a performance snapshots
o Get a list of snapshots
select SNAP_ID, SNAP_TIME from STATS$SNAPSHOT;
@spreport.sql -- Enter two snapshot id's for difference report
Other Statspack Scripts:
. sppurge.sql - Purge a range of Snapshot Id's between the specified begin and end Snap Id's
. spauto.sql - Schedule a dbms_job to automate the collection of STATPACK statistics
. spcreate.sql - Installs the STATSPACK user, tables and package on a database (Run as SYS).
. spdrop.sql - Deinstall STATSPACK from database (Run as SYS)
. sppurge.sql - Delete a range of Snapshot Id's from the database
. spreport.sql - Report on differences between values recorded in two snapshots
. sptrunc.sql - Truncates all data in Statspack tables
95. What are the common RMAN errors (with solutions)? (for DBA
Some of the common RMAN errors are:
RMAN-20242: Specification does not match any archivelog in the recovery catalog.
Add to RMAN script: sql 'alter system archive log current';
RMAN-06089: archived log xyz not found or out of sync with catalog
Execute from RMAN: change archivelog all validate;
96. How can you execute the user defined triggers in forms 3.0 ?
Execute Trigger (trigger-name)
97. What ERASE package procedure does ?
Erase removes an indicated global variable.
98. What is the difference between NAME_IN and COPY ?
Copy is package procedure and writes values into a field.
Name in is a package function and returns the contents of the variable to which you apply.
99. What package procedure is used for calling another form ?
Call (E.g. Call(formname)
100. When the form is running in DEBUG mode, If you want to examine the values of global variables and other form variables, What package procedure command you would use in your trigger text ?
The value recorded in system.last_record variable is of type
c. Character. ?
101. What is mean by Program Global Area (PGA) ?
It is area in memory that is used by a Single Oracle User Process.
102. What is hit ratio ?
It is a measure of well the data cache buffer is handling requests for data. Hit Ratio = (Logical Reads - Physical Reads - Hits Misses)/ Logical Reads.
103. How do you implement the If statement in the Select Statement
We can implement the if statement in the select statement by using the Decode statement. e.g select DECODE (EMP_CAT,'1','First','2','Second'Null); Here the Null is the else statement where null is done
104. How many types of Exceptions are there
There are 2 types of exceptions. They are
a) System Exceptions
e.g. When no_data_found, When too_many_rows
b) User Defined Exceptions
e.g. My_exception exception
When My_exception then
105. What are the inline and the precompiler directives
The inline and precompiler directives detect the values directly
106. How do you use the same lov for 2 columns
We can use the same lov for 2 columns by passing the return values in global values and using the global values in the code
107. How many minimum groups are required for a matrix report
The minimum number of groups in matrix report are 4
108. What is the difference between static and dynamic lov
The static lov contains the predetermined values while the dynamic lov contains values that come at run time
109. How does one manage Oracle database users? (for DBA
Oracle user accounts can be locked, unlocked, forced to choose new passwords, etc. For example, all accounts except SYS and SYSTEM will be locked after creating an Oracle9iDB database using the DB Configuration Assistant (dbca). DBA's must unlock these accounts to make them available to users.
Look at these examples:
ALTER USER scott ACCOUNT LOCK -- lock a user account
ALTER USER scott ACCOUNT UNLOCK; -- unlocks a locked users account
ALTER USER scott PASSWORD EXPIRE; -- Force user to choose a new password
110. How does one tune Oracle Wait events? (for DBA
Some wait events from V$SESSION_WAIT and V$SYSTEM_EVENT views:
Event Name: Tuning Recommendation:
db file sequential read Tune SQL to do less I/O. Make sure all objects are analyzed. Redistribute I/O across disks.
buffer busy waits Increase DB_CACHE_SIZE (DB_BLOCK_BUFFERS prior to 9i)/ Analyze contention from SYS.V$BH
log buffer spaces Increase LOG_BUFFER parameter or move log files to faster disks
111. What is the difference between DBFile Sequential and Scattered Reads? (for DBA
Both "db file sequential read" and "db file scattered read" events signify time waited for I/O read requests to complete. Time is reported in 100's of a second for Oracle 8i releases and below, and 1000's of a second for Oracle 9i and above. Most people confuse these events with each other as they think of how data is read from disk. Instead they should think of how data is read into the SGA buffer cache.
db file sequential read:
A sequential read operation reads data into contiguous memory (usually a single-block read with p3=1, but can be multiple blocks). Single block I/Os are usually the result of using indexes. This event is also used for rebuilding the controlfile and reading datafile headers (P2=1). In general, this event is indicative of disk contention on index reads.
db file scattered read:
Similar to db file sequential reads, except that the session is reading multiple data blocks and scatters them into different discontinuous buffers in the SGA. This statistic is NORMALLY indicating disk contention on full table scans. Rarely, data from full table scans could be fitted into a contiguous buffer area, these waits would then show up as sequential reads instead of scattered reads.
The following query shows average wait time for sequential versus scattered reads:
prompt "AVERAGE WAIT TIME FOR READ REQUESTS"
select a.average_wait "SEQ READ", b.average_wait "SCAT READ"
from sys.v_$system_event a, sys.v_$system_event b
where a.event = 'db file sequential read'
and b.event = 'db file scattered read';
112. What is the use of PARFILE option in EXP command ?
Name of the parameter file to be passed for export.
113. What is the use of TABLES option in EXP command ?
List of tables should be exported.ze
114. What is the OPTIMAL parameter?
It is used to set the optimal length of a rollback segment.
115. How does one use ORADEBUG from Server Manager/ SQL*Plus? (for DBA
Execute the "ORADEBUG HELP" command from svrmgrl or sqlplus to obtain a list of valid ORADEBUG commands. Look at these examples:
SQLPLUS> REM Trace SQL statements with bind variables
SQLPLUS> oradebug setospid 10121
Oracle pid: 91, Unix process pid: 10121, image: oracleorcl
SQLPLUS> oradebug EVENT 10046 trace name context forever, level 12
SQLPLUS> ! vi /app/oracle/admin/orcl/bdump/ora_10121.trc
SQLPLUS> REM Trace Process Statistics
SQLPLUS> oradebug setorapid 2
Unix process pid: 1436, image: ora_pmon_orcl
SQLPLUS> oradebug procstat
SQLPLUS>> oradebug TRACEFILE_NAME
SQLPLUS> REM List semaphores and shared memory segments in use
SQLPLUS> oradebug ipc
SQLPLUS> REM Dump Error Stack
SQLPLUS> oradebug setospid <pid>
SQLPLUS> oradebug event immediate trace name errorstack level 3
SQLPLUS> REM Dump Parallel Server DLM locks
SQLPLUS> oradebug lkdebug -a convlock
SQLPLUS> oradebug lkdebug -a convres
SQLPLUS> oradebug lkdebug -r <resource handle> (i.e 0x8066d338 from convres dump)
116. Are there any undocumented commands in Oracle? (for DBA
Sure there are, but it is hard to find them. Look at these examples:
From Server Manager (Oracle7.3 and above): ORADEBUG HELP
It looks like one can change memory locations with the ORADEBUG POKE command. Anyone brave enough to test this one for us? Previously this functionality was available with ORADBX (ls -l $ORACLE_HOME/rdbms/lib/oradbx.o; make -f oracle.mk oradbx) SQL*Plus: ALTER SESSION SET CURRENT_SCHEMA = SYS;
117. If the maximum record retrieved property of the query is set to 10 then a summary value will be calculated?
Only for 10 records.
118. What are the different objects that you cannot copy or reference in object groups?
Objects of different modules
Another object groups
Individual block dependent items
119. What is an OLE?
Object Linking & Embedding provides you with the capability to integrate objects from many Ms-Windows applications into a single compound document creating integrated applications enables you to use the features form .
120. Can a repeating frame be created without a data group as a base?
121. Is it possible to set a filter condition in a cross product group in matrix reports?
122. What is Overloading of procedures ?
The Same procedure name is repeated with parameters of different datatypes and parameters in different positions, varying number of parameters is called overloading of procedures. e.g. DBMS_OUTPUT put_line
123. What are the return values of functions SQLCODE and SQLERRM ? What is Pragma EXECPTION_INIT ? Explain the usage ?
SQLCODE returns the latest code of the error that has occurred.
SQLERRM returns the relevant error message of the SQLCODE.
124. What are the datatypes a available in PL/SQL ?
Some scalar data types such as NUMBER, VARCHAR2, DATE, CHAR, LONG, BOOLEAN. Some composite data types such as RECORD & TABLE.
125. What are the two parts of a procedure ?
Procedure Specification and Procedure Body.
126. What is the basic structure of PL/SQL ?
PL/SQL uses block structure as its basic structure. Anonymous blocks or nested blocks can be used in PL/SQL.
127. What is PL/SQL table ?
Objects of type TABLE are called "PL/SQL tables", which are modeled as (but not the same as) database tables, PL/SQL tables use a primary PL/SQL tables can have one column and a primary key. Cursors
128. WHAT IS RMAN ? (for DBA
Recovery Manager is a tool that: manages the process of creating backups and also manages the process of restoring and recovering from them.
129. WHY USE RMAN ? (for DBA
1.No extra costs …Its available free
2.?RMAN introduced in Oracle 8 it has become simpler with newer versions and easier than user managed backups
4.?You are 100% sure your database has been backed up.
5.?Its contains detail of the backups taken etc in its central repository
6.Facility for testing validity of backups also commands like crosscheck to check the status of backup.
7.Faster backups and restores compared to backups without RMAN
8.RMAN is the only backup tool which supports incremental backups.
9.Oracle 10g has got further optimized incremental backup which has resulted in improvement of performance during backup and recovery time
10.Parallel operations are supported
11.Better querying facility for knowing different details of backup
12.No extra redo generated when backup is taken..compared to online
13.backup without RMAN which results in saving of space in hard disk
14.RMAN an intelligent tool
15.Maintains repository of backup metadata
16.Remembers backup set location
17.Knows what need to backed up
18.Knows what is required for recovery
19.Knows what backups are redundant
UNDERSTANDING THE RMAN ARCHITECTURE
An oracle RMAN comprises of
RMAN EXECUTABLE This could be present and fired even through client side
TARGET DATABASE This is the database which needs to be backed up .
RECOVERY CATALOG Recovery catalog is optional otherwise backup details are stored in target database controlfile.
It is a repository of information queried and updated by Recovery Manager
It is a schema or user stored in Oracle database. One schema can support many databases
It contains information about physical schema of target database datafile and archive log ,backup sets and pieces Recovery catalog is a must in following scenarios
. In order to store scripts
. For tablespace point in time recovery
Media Management Software
Media Management software is a must if you are using RMAN for storing backup in tape drive directly.
Backups in RMAN
Oracle backups in RMAN are of the following type
RMAN complete backup OR RMAN incremental backup
These backups are of RMAN proprietary nature
The advantage of uing Image copy is its not in RMAN proprietary format..
RMAN backup is not in oracle format but in RMAN format. Oracle backup comprises of backup sets and it consists of backup pieces. Backup sets are logical entity In oracle 9i it gets stored in a default location There are two type of backup sets Datafile backup sets, Archivelog backup sets One more important point of data file backup sets is it do not include empty blocks. A backup set would contain many backup pieces.
A single backup piece consists of physical files which are in RMAN proprietary format.
Example of taking backup using RMAN
Taking RMAN Backup
In non archive mode in dos prompt type
You get the RMAN prompt
RMAN > Connect Target
Connect to target database : Magic
using target database controlfile instead of recovery catalog
Lets take a simple backup of database in non archive mode
shutdown immediate ; - - Shutdowns the database
backup database ;- its start backing the database
alter database open;
We can fire the same command in archive log mode
And whole of datafiles will be backed
Backup database plus archivelog;
Restoring database has been made very simple in 9i .
It is just
RMAN has become intelligent to identify which datafiles has to be restored
and the location of backuped up file.
Oracle Enhancement for RMAN in 10 G
Flash Recovery Area
Right now the price of hard disk is falling. Many dba are taking oracle database backup inside the hard disk itself since it results in lesser mean time between recoverability.
The new parameter introduced is
DB_RECOVERY_FILE_DEST = /oracle/flash_recovery_area
By configuring the RMAN RETENTION POLICY the flash recovery area will automatically delete obsolete backups and archive logs that are no longer required based on that configuration Oracle has introduced new features in incremental backup
Change Tracking File
Oracle 10g has the facility to deliver faster incrementals with the implementation of changed tracking file feature.This will results in faster backups lesser space consumption and also reduces the time needed for daily backups
Incrementally Updated Backups
Oracle database 10g Incrementally Updates Backup features merges the image copy of a datafile with RMAN incremental backup. The resulting image copy is now updated with block changes captured by incremental backups.The merging of the image copy and incremental backup is initiated with RMAN recover command. This results in faster recovery.
Binary compression technique reduces backup space usage by 50-75%.
With the new DURATION option for the RMAN BACKUP command, DBAs can weigh backup performance against system service level requirements. By specifying a duration, RMAN will automatically calculate the appropriate backup rate; in addition, DBAs can optionally specify whether backups should minimize time or system load.
New Features in Oem to identify RMAN related backup like backup pieces, backup sets and image copy
Oracle 9i New features Persistent RMAN Configuration
A new configure command has been introduced in Oracle 9i , that lets you configure various features including automatic channels, parallelism ,backup options, etc.
These automatic allocations and options can be overridden by commands in a RMAN command file.
Controlfile Auto backups
Through this new feature RMAN will automatically perform a controlfile auto backup. after every backup or copy command.
Block Media Recovery
If we can restore a few blocks rather than an entire file we only need few blocks.
We even dont need to bring the data file offline.
Syntax for it as follows
Block Recover datafile 8 block 22;
Configure Backup Optimization
Prior to 9i whenever we backed up database using RMAN our backup also used take backup of read only table spaces which had already been backed up and also the same with archive log too.
Now with 9i backup optimization parameter we can prevent repeat backup of read only tablespace and archive log. The command for this is as follows Configure backup optimization on
Archive Log failover
If RMAN cannot read a block in an archived log from a destination. RMAN automatically attempts to read from an alternate location this is called as archive log failover
There are additional commands like
backup database not backed up since time '31-jan-2002 14:00:00'
Do not backup previously backed up files
(say a previous backup failed and you want to restart from where it left off).
Similar syntax is supported for restores
backup device sbt backup set all Copy a disk backup to tape
(backing up a backup
Additionally it supports
. Backup of server parameter file
. Parallel operation supported
. Extensive reporting available
. Duplex backup sets
. Corrupt block detection
. Backup archive logs
Pitfalls of using RMAN
Previous to version Oracle 9i backups were not that easy which means you had to allocate a channel compulsorily to take backup You had to give a run etc . The syntax was a bit complex …RMAN has now become very simple and easy to use..
If you changed the location of backup set it is compulsory for you to register it using RMAN or while you are trying to restore backup It resulted in hanging situations
There is no method to know whether during recovery database restore is going to fail because of missing archive log file.
Compulsory Media Management only if using tape backup
Incremental backups though used to consume less space used to be slower since it used to read the entire database to find the changed blocks and also They have difficult time streaming the tape device. .
Considerable improvement has been made in 10g to optimize the algorithm to handle changed block.
Introduced in Oracle 8 it has become more powerful and simpler with newer version of Oracle 9 and 10 g.
So if you really don't want to miss something critical please start using RMAN.
130. Explain UNION,MINUS,UNION ALL, INTERSECT ?
INTERSECT returns all distinct rows selected by both queries.MINUS - returns all distinct rows selected by the first query but not by the second.UNION - returns all distinct rows selected by either queryUNION ALL - returns all rows selected by either query, including all duplicates.
131. Should the OEM Console be displayed at all times (when there are scheduled jobs)? (for DBA
When a job is submitted the agent will confirm the status of the job. When the status shows up as scheduled, you can close down the OEM console. The processing of the job is managed by the OIA (Oracle Intelligent Agent). The OIA maintains a .jou file in the agent's subdirectory. When the console is launched communication with the Agent is established and the contents of the .jou file (binary) are reported to the console job subsystem. Note that OEM will not be able to send e-mail and paging notifications when the Console is not started.
132. Difference between SUBSTR and INSTR ?
INSTR (String1,String2(n,(m)),INSTR returns the position of the mth occurrence of the string 2 instring1. The search begins from nth position of string1.SUBSTR (String1 n,m)SUBSTR returns a character string of size m in string1, starting from nth position of string1.
133. What kind of jobs can one schedule with OEM? (for DBA
OEM comes with pre-defined jobs like Export, Import, run OS commands, run sql scripts, SQL*Plus commands etc. It also gives you the flexibility of scheduling custom jobs written with the TCL language.
134. What are the pre requisites ?
I. to modify data type of a column ? ii. to add a column with NOT NULL constraint ? To Modify the datatype of a column the column must be empty. to add a column with NOT NULL constrain, the table must be empty.
135. How does one backout events and jobs during maintenance slots? (for DBA
Managemnet and data collection activity can be suspended by imposing a blackout. Look at these examples:
agentctl start blackout # Blackout the entrire agent
agentctl stop blackout # Resume normal monitoring and management
agentctl start blackout ORCL # Blackout database ORCL
agentctl stop blackout ORCL # Resume normal monitoring and management
agentctl start blackout -s jobs -d 00:20 # Blackout jobs for 20 minutes
136. What are the types of SQL Statement ?
Data Definition Language :
CREATE,ALTER,DROP,TRUNCATE,REVOKE,NO AUDIT & COMMIT.
Data Manipulation Language:
TABLE,EXPLAIN PLAN & SELECT.Transactional Control:
COMMIT & ROLLBACKSession Control: ALTERSESSION & SET
ROLESystem Control :
137. What is the Oracle Intelligent Agent? (for DBA
The Oracle Intelligent Agent (OIA) is an autonomous process that needs to run on a remote node in the network to make the node OEM manageable. The Oracle Intelligent Agent is responsible for:
. Discovering targets that can be managed (Database Servers, Net8 Listeners, etc.);
. Monitoring of events registered in Enterprise Manager; and
. Executing tasks associated with jobs submitted to Enterprise Manager.
138. How does one start the Oracle Intelligent Agent? (for DBA
One needs to start an OIA (Oracle Intelligent Agent) process on all machines that will to be managed via OEM.
For OEM 9i and above:
agentctl start agent
agentctl stop agent
For OEM 2.1 and below:
On Windows NT, start the "OracleAgent" Service.
If the agent doesn't want to start, ensure your environment variables are set correctly and delete the following files before trying again:
1) In $ORACLE_HOME/network/admin: snmp_ro.ora and snmp_rw.ora.
2) Also delete ALL files in $ORACLE_HOME/network/agent/.
Can one write scripts to send alert messages to the console?
Start the OEM console and create a new event. Select option "Enable Unsolicited Event". Select test "Unsolicited Event". When entering the parameters, enter values similar to these:
Event Name: /oracle/script/myalert
One can now write the script and invoke the oemevent command to send alerts to the console. Look at this example: oemevent /oracle/script/myalert DESTINATION alert "My custom error message" where DESTINATION is the same value as entered in the "Monitored Destinations" field when you've registered the event in the OEM Console.
860. Where can one get more information about TCL? (for DBA
One can write custom event checking routines for OEM using the TCL (Tool Command Language) language. Check the following sites for more information about TCL:
. The Tcl Developer Xchange - download and learn about TCL
. OraTCL at Sourceforge - Download the OraTCL package
. Tom Poindexter's Tcl Page - Oratcl was originally written by Tom Poindexter
139. Are there any troubleshooting tips for OEM? (for DBA
Create the OEM repository with a user (which will manage the OEM) and store it in a tablespace that does not share any data with other database users. It is a bad practice to create the repository with SYS and System.
. If you are unable to launch the console or there is a communication problem with the intelligent agent (daemon). Ensure OCX files are registered. Type the following in the DOS prompt (the current directory should be $ORACLE_HOMEBIN:
C:Orawin95Bin> RegSvr32 mmdx32.OCX
C:Orawin95Bin> RegSvr32 vojt.OCX
. If you have a problem starting the Oracle Agent
Solution A: Backup the *.Q files and Delete all the *.Q Files ($Oracle_home/network/agent folder)
Backup and delete SNMP_RO.ora, SNMP_RW.ora, dbsnmp.ver and services.ora files ($Oracle_Home/network/admin folder) Start the Oracle Agent service.
Solution B: Your version of Intelligent Agent could be buggy. Check with Oracle for any available patches. For example, the Intelligent Agent that comes with Oracle 8.0.4 is buggy.
Sometimes you get a Failed status for the job that was executed successfully.
Check the log to see the results of the execution rather than relying on this status.
140. What is import/export and why does one need it? (for DBA
The Oracle export (EXP) and import (IMP) utilities are used to perform logical database backup and recovery. They are also used to move Oracle data from one machine, database or schema to another.
The imp/exp utilities use an Oracle proprietary binary file format and can thus only be used between Oracle databases. One cannot export data and expect to import it into a non-Oracle database. For more information on how to load and unload data from files, read the SQL*Loader FAQ.
The export/import utilities are also commonly used to perform the following tasks:
. Backup and recovery (small databases only)
. Reorganization of data/ Eliminate database fragmentation
. Detect database corruption. Ensure that all the data can be read.
. Transporting tablespaces between databases
141. 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.
142. How does one use the import/export utilities? (for DBA
Look for the "imp" and "exp" executables in your $ORACLE_HOME/bin directory. One can run them interactively, using command line parameters, or using parameter files. Look at the imp/exp parameters before starting. These parameters can be listed by executing the following commands: "exp help=yes" or "imp help=yes".
The following examples demonstrate how the imp/exp utilities can be used:
exp scott/tiger file=emp.dmp log=emp.log tables=emp rows=yes indexes=no
exp scott/tiger file=emp.dmp tables=(emp,dept)
imp scott/tiger file=emp.dmp full=yes
imp scott/tiger file=emp.dmp fromuser=scott touser=scott tables=dept
exp userid=scott/tiger@orcl parfile=export.txt
... where export.txt contains:
NOTE: If you do not like command line utilities, you can import and export data with the "Schema Manager" GUI that ships with Oracle Enterprise Manager (OEM).
143. What are the types of visual attribute settings?
Custom Visual attributes Default visual attributes Named Visual attributes. Window
144. Can one export a subset of a table? (for DBA
From Oracle8i one can use the QUERY= export parameter to selectively unload a subset of the data from a table. Look at this example:
exp scott/tiger tables=emp query="where deptno=10"
145. What are the two ways to incorporate images into a oracle forms application?
146. Can one monitor how fast a table is imported? (for DBA
If you need to monitor how fast rows are imported from a running import job, try one of the following methods:
select substr(sql_text,instr(sql_text,'INTO "'),30) table_name,
round((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60,1) minutes,
trunc(rows_processed/((sysdate-to_date(first_load_time,'yyyy-mm-dd hh24:mi:ss'))*24*60)) rows_per_min
where sql_text like 'INSERT %INTO "%'
and command_type = 2
and open_versions > 0;
For this to work one needs to be on Oracle 7.3 or higher (7.2 might also be OK). If the import has more than one table, this statement will only show information about the current table being imported.
Contributed by Osvaldo Ancarola, Bs. As. Argentina.
Use the FEEDBACK=n import parameter. This command will tell IMP to display a dot for every N rows imported.
147. Can one import tables to a different tablespace? (for DBA
Oracle offers no parameter to specify a different tablespace to import data into. Objects will be re-created in the tablespace they were originally exported from. One can alter this behaviour by following one of these procedures: Pre-create the table(s) in the correct tablespace:
. Import the dump file using the INDEXFILE= option
. Edit the indexfile. Remove remarks and specify the correct tablespaces.
. Run this indexfile against your database, this will create the required tables in the appropriate tablespaces
. Import the table(s) with the IGNORE=Y option.
Change the default tablespace for the user:
. Revoke the "UNLIMITED TABLESPACE" privilege from the user
. Revoke the user's quota from the tablespace from where the object was exported. This forces the import utility to create tables in the user's default tablespace.
. Make the tablespace to which you want to import the default tablespace for the user
. Import the table
148. 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.
149. 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.
150. How is possible to restrict the user to a list of values while entering values for parameters?
By setting the Restrict To List property to true in the parameter property sheet.
151. What is SQL*Loader and what is it used for? (for DBA
SQL*Loader is a bulk loader utility used for moving data from external files into the Oracle database. Its syntax is similar to that of the DB2 Load utility, but comes with more options. SQL*Loader supports various load formats, selective loading, and multi-table loads.
152. How does one use the SQL*Loader utility? (for DBA
One can load data into an Oracle database by using the sqlldr (sqlload on some platforms) utility. Invoke the utility without arguments to get a list of available parameters. Look at the following example:
sqlldr scott/tiger control=loader.ctl
This sample control file (loader.ctl) will load an external data file containing delimited data:
into table emp
fields terminated by "," optionally enclosed by '"'
( empno, empname, sal, deptno )
The mydata.csv file may look like this:
10001,"Scott Tiger", 1000, 40
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