Q : What is Level 0, Level 1 backup?
A : A level 0 incremental backup, which is the base for subsequent incremental backups, copies all blocks containing data, backing the data file up into a backup set just as a full backup would. A level 1 incremental backup can be either of the following types:
A differential backup, which backs up all blocks changed after the most recent incremental backup at level 1 or 0
A cumulative backup, which backs up all blocks changed after the most recent incremental backup at level 0
Q : How do you setup the RMAN tape backups?
A : Configure channel as SBT_TAPE and use “ENV” parameter to set the tape configurations.
Q : What is the init parameter specify the minimum number of days that Oracle keeps backup information in the control file?
A : You can use the CONTROL_FILE_RECORD_KEEP_TIME parameter to specify the minimum number of days that Oracle keeps this information in the control file.
Q : What is the difference between validate and crosscheck ?
A : The restore … validate and validate backupset commands test whether you can restore backups or copies. You should use:
– restore : validate when you want RMAN to choose which backups or copies should be tested.
– validate backupset when you want to specify which backup sets should be tested.
Q : How do I go about backing up my online redo logs?
A : Online redo logs should never, ever be included in a backup, regardless of whether that backup is performed hot or cold. The reasons for this are two-fold. First, you physically cannot backup a hot online redo log, and second there is precisely zero need to do so in the first place because an archive redo log is, by definition, a backup copy of a formerly on-line log. There is, however, a more practical reason: backing up the online logs yourself increases the risk that you will lose
Q : What is backup set?
A : RMAN can store backup data in a logical structure called a backup set, which is the smallest unit of an RMAN backup. A backup set contains the data from one or more data files, archived redo logs, or control files or server parameter file.
Q : What is Channel? How do you enable the parallel backups with RMAN?
A : Use the ALLOCATE CHANNEL command to manually allocate a channel, which is a connection between RMAN and a database instance. To enable the parallel backups, allocate multiple manual channels in the run block or configure parallelism
CONFIGURE DEVICE TYPE DISK PARALLELISM 4 BACKUP TYPE TO BACKUPSET;
Q : What is auxiliary channel in RMAN? When do you need this?
A : An auxiliary channel is a link to auxiliary instance. If you do not have automatic channels configured, then before issuing the DUPLICATE command, manually allocate at least one auxiliary channel within the same RUN command. When a Duplicate Database created or table space point in time recovery is performed Auxiliary database is used. This database can either on the same host or a different host.
Is it possible to specific tables when using RMAN DUPLICATE feature? If yes, how?
No, table based recovery not possible in RMAN duplicate command.
Q : Outline the steps involved in CANCEL based recovery from the full database from hot backup?
A : RMAN doesn’t support cancel-based recovery like SQL*plus does.
Q : Outline the steps involved in SCN based recovery from the full database from hot backup?
A : startup mount;
restore database UNTIL SCN 233545;
recover database UNTIL SCN 233545;
alter database open resetlogs;
Q : How do you verify the integrity of the image copy in RMAN environment?
A : Use below commands :
rman> catalog datafilecopy ‘f:testsystem.dbf’;
rman> backup validate check logical datafile ‘f:testsystem.dbf’;
SQL> SELECT * FROM v$database_block_corruption;
Q : Is it possible to take Catalog Database Backup using RMAN? If Yes, How?
A : A recovery catalog is a schema stored in a database that tracks backups and stores of target databases. So better to take a export backup How do you identify the expired, active, obsolete backups? Which RMAN command you use?
Obsolete backups:
RMAN> report obsolete;
expired backup:
RMAN> list expired backup;
Active database: RMAN> list backup;
Q : Outline the steps involved in TIME based recovery from the full database from hot backup?
A : startup mount;
restore database UNTIL TIME “TO_DATE(’28/12/2012 18:00:00?, ‘DD/MM/YYYY HH24:MI:SS’)”;
recover database UNTIL TIME “TO_DATE(’28/12/2012 18:00:00?, ‘DD/MM/YYYY HH24:MI:SS’)”;
alter database open resetlogs;
Q : Explain the steps to perform the point in time recovery with a backup which is taken before the resetlogs of the db?
A :
- We need to list the database incarnations by using list incarnation command.
- shutdown the database
- startup mount the database
- Issue reset database to incarnation to reset the incarnation.
- Restore the database using restore command (e.g restore until scn 23243)
- recover database
- Open the database using resetlogs command
RMAN> list incarnation of database;
RMAN>reset database to incarnation 5;
run
{
set until scn 234345;
restore database;
rec ….
Q : Outline the steps for changing the DBID in a cloned environment?
A : shutdown Immediate
startup mount
Then, run the the DBNEWID utility from command line.
nid target =/
SQL> alter database open resetlogs;
Q : How do you install the RMAN recovery catalog? or List the steps required to enable the RMAN . backup for a target database?
A : Steps to be followed:
1) Create connection string at catalog database.
2) At catalog database create one new user or use existing user and give that user a recovery_catalog_owner privilege.
3) Login into RMAN with connection string
- export ORACLE_SID
- rman target catalog @connection string
4) rman&g ….
Q : List some of the RMAN catalog view names which contain the catalog information?
A : RC_DATABASE_INCARNATION, RC_BACKUP_COPY_DETAILS, RC_BACKUP_CORRUPTION, RC_BACKUP_DATAFILE_SUMMARY to name a few
Q : What is the difference between obsolete RMAN backups and expired RMAN backups?
A : The term obsolete does not mean the same as expired. In short obsolete means “not needed ” whereas expired means “not found.”
A status of “expired” means that the backup piece or backup set is not found in the backup destination. A status of “obsolete” means the backup piece is still available, but it is no longer needed. The backup piece is no longer needed since RMAN has been configured to no longer need this piece after so many days have elapsed, or so many backups have been performed. ….
Q : When do you use crosscheck command?
A : Crosscheck will be useful to check whether the catalog information is intact with OS level information.
Q : How do you clone the database using RMAN? Give brief steps
A : Two commands available in RMAN to clone database:
- Duplicate target database to …
- Restore.
Q : How do you identify the block corruption in RMAN database? How do you fix it?
A : Typically, block corruption is reported in the following locations:
Results of the LIST FAILURE, VALIDATE, or BACKUP … VALIDATE command
The V$DATABASE_BLOCK_CORRUPTION view
Error messages in standard output
The alert log
User trace files
Results of the SQL commands ANALYZE TABLE and ANALYZE INDEX
Results of the DBVERIFY utility
Third-party media management output
& ….
Q : What is the difference between cumulative incremental and differential incremental backups?
A : Differencial backup: This is the default type of incremental backup which backs up all blocks changed after the most recent backup at level n or lower. Cumulative backup: Backup all blocks cahnged after the most recent backup at level n-1 or lower.
Q : How do you enable the autobackup for the controlfile using RMAN?
A : issue command at rman prompt…..
RMAN> configure controlfile autobackup on;
also we can configure controlfile backup format……
RMAN> configure controlfile autobackup format for device type disk to ‘$HOME/BACKUP/RMAN/ F.bkp’; — $HOME/BACKUP/RMAN/ this can be any desired location.
Q : How RMAN improves backup time?
A : RMAN backup time consumption is very less than compared to regular online backup as RMAN copies only modified blocks
Q : How do you monitor RMAN backup job status.
A : Use this SQL to check
SQL> SELECT sid totalwork sofar FROM v$session_longops WHERE sid 153;
Here give SID when back start it will show SID
Q : How do you see information about backups in RMAN?
A : RMAN> List Backup;
Q : What is the diff between CATALOG vs NOCATALOG
A : The difference is only who maintains the backup records like when is the last successful backup incremental differential etc.
- In CATALOG mode another database (TARGET database) stores all the information.
- In NOCATALOG mode controlfile of Target database is responsible.
Q : Where RMAN keeps information of backups if you are using RMAN without Catalog?
A : RMAN keeps information of backups in the control file.
Q : You have taken a manual backup of a datafile using o/s. How RMAN will know about it? or How to put manual/user-managed backup in RMAN (recovery catalog)?
A : By using catalog command. You have to catalog that manual backup in RMAN’s repository by command
RMAN> catalog datafilecopy ‘/DB01/BACKUP/users01.dbf’;
or
RMAN> CATALOG START WITH ‘/tmp/backup.ctl’;
Restrictions:
> Accessible on disk
> A complete image copy of a single file
Q : If some of the blocks are corrupted due to system crash, How will you recover?
A : Using RMAN BLOCK RECOVER command