Sunday, 29 April 2018

Oracle RMAN Interview Questions and Answers




Hi DBA-mates,
After long time, again we are back with some important RMAN Questions and Answers. Now a day it is very important to know about the RMAN details and Configurations.

As per technologies changes, we should also upgrade our self. Now a day’s RMAN is asking in every profile.
I have selected some very important Questions and Answers as per my experiences and I have some more questions which I will be including here soon.

Q1.What is RMAN ?
A.RMAN is an Oracle Database client that performs backup and recovery tasks on your databases and automates administration of your backup strategies.
It greatly simplifies the dba jobs by managing the production database's backing up, restoring, and recovering database files.

Q2.Why to use RMAN ?
A.RMAN gives you access to several backup and recovery techniques and features not available with user-managed backup and recovery. The most noteworthy are the following:
-- Automatic specification of files to include in a backup :  Establishes the name and locations of all files to be backed up.
-- Maintain backup repository:  Backups are recorded in the control file, which is the main repository of RMAN metadata.  Additionally, you can store this metadata in a recovery catalog.
-- Incremental backups: An incremental backup stores only blocks changed since a previous backup.
Thus, they provide more compact backups and faster recovery, thereby reducing the need to apply redo during datafile media recovery.

-- Unused block compression  :  In unused block compression, RMAN can skip data blocks that have never been used
-- Block media recovery: You an repair a datafile with only a small number of corrupt data blocks without taking it offline or restoring it from backup.
-- Binary compression: A binary compression mechanism integrated into Oracle Database reduces the size of backups.
-- Encrypted backups : RMAN uses backup encryption capabilities integrated into Oracle Database to store backup sets in an encrypted format.
-- Corrupt block detection :  RMAN checks for the block corruption before taking its backup.

Q3.How to check RMAN Configuration ?
RMAN>Show all;

Q4.How to Reset to default Configuration ?

A.To reset the default configuration setting use Connect to the target database from sqlplus and run
SQL> connect <sys/passwd as sysdba>@target_database; 
SQL> execute dbms_backup_restore.resetConfig;

Q5. How Many catalog database I can have ?
A.  You can have multiple catalog database for the same target database . But at a time you can connect to only 1 catalog database via RMAN. It’s not recommended to have multiple catalog databases.

Q6. Is this mandatory to use catalog database ?
A.  No ! it’s a optional one.

Q7. What is the difference between catalog database & catalog schema ?
A.  Catalog database is like any other database which contains the RMAN catalog user's schema.

Q8. What are the database file's that RMAN can backup ?
A. RMAN can backup  Controlfile , Datafiles , Archive logs , standby database controfile, Spfile

Q9. What are the database file's that RMAN cannot backup ?
A.  RMAN cannot take backup of the pfile, Redo logs , network configuration files, password files, external  tables and the contents of the Oracle home files

Q10. Can I have archivelogs and datafile backup in a single backupset ?
A.  No . we can not put datafiles and archive logs in the same backupset.

Q11. What is the difference between backup set backup and Image copy backup ?
A :  A backup set is an RMAN-specific proprietary format, whereas an image copy is a bit-for-bit copy of a file. By default, RMAN creates backup sets

Q12. Can I take RMAN backup when the database is Down ?
A. No ! You can take RMAN backup only when the target database is Open or in Mount stage. Its because RMAN keep the backup metadata in controfile . Only in open or mount mode controlfile is accessible.

Note: We will Provide Duplicate RMAN backup and Restore soon…

Some Important links:






Hope this may useful and helpful. For any concerns please let us know either in comment box or contact @ora-data.blogspot.com
ref. doc:469777.1

Regards,
ora-data Team

Sunday, 4 March 2018

Oracle Apps Interviews Technical Questions and Answers by MNC Compnaies

Hi DBA-mates,
We are back again with some important Questions which may useful and helpful for any interviews.
I got these Questions from a friend, so I thought to share and it might useful here for all.
Actually, these questions are not for Oracle Apps DBA. These questions are looks like for Oracle DBA (Core).

1. Introduced yourself and your role.

2. How to disable archive log:
Ans. The method for disabling archive log mode described above is the only way to disable archive log mode.

Shutdown edit pfile / spfile (spfile when instance is up of course) to say log_archive_start = false.

startup mount

alter database noarchivelog;

alter database open;


Remember that once you disable archive log mode you need to take a fresh backup once archive log mode is turned back on.

3. RMAN Configuration:

rman>show all ;                                                 ## to check all the configuration.

RMAN> configure controlfile autobackup on;    # for on and off
RMAN> configure backup optimization off;

4. How to check database alert log path?
Ans:
If database if UP and Running:
SQL> show parameters dump

Or SELECT * FROM v$daig_info;

If database is down:
Or you can check as from ps –ef|grep tns then follow the paths…
i.e go till oracle_home (oracle version)
then $ORACEL_HOME/admin/SID_Hostname/diag/rdbms/sid/SID/trace

ls –l alert*
alert_SID.log


5. How to check Table log? (i.e. Logging and Nologging concepts) # not sure

6. How to check blocking session?
Ans:
$ cat block.sql
select sid "Session id ", decode(Block,1, 'Blocking Session','Waiting Session') Details, ctime  "Blocking Time /Waiting time",id2 from v$lock where (block <> 0 or request <>0 ) and ctime > 200 order by id2,Details;

SQL> desc v$lock
 Name                                      Null?    Type
 ----------------------------------------- -------- ----------------------------
 ADDR                                               RAW(8)
 KADDR                                              RAW(8)
 SID                                                NUMBER
 TYPE                                               VARCHAR2(2)
 ID1                                                NUMBER
 ID2                                                NUMBER
 LMODE                                              NUMBER
 REQUEST                                            NUMBER
 CTIME                                              NUMBER
 BLOCK                                              NUMBER

SQL>

7. How to do expdp and impdp details and concepts.

Ans:


8. How to Apply Database Patches.

Ans:
9. How to Apply Apps patches apply.

Ans:


Some more Questions and Answers by Top MNC Companies coming soon...

Regards,
Ora-data Team