RMAN INTERVIEW QUESTIONS AND ANSWERS
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51.
How to perform the cancel based recovery
from the full database via hot
backup?
CANCEL
BASED RECOVERY
Cancel base recovery allows the DBA to cancel recovery at a desired point.
This situation is most likely occur if archive logfiles or redo logfiles needed
for recovery are lost or damaged and cannot be restored. In this situation, you
would apply all logs until you reached the missing files and then cancel the recovery
FOLLOW
THES STEPS TO EXECUTE A CANCEL BASED RECOVERY
A). If the
database is still open, shut down
the database using the shutdown command
with the ABORT option.
B). Make a full backup of the database, including all datafiles, a control
file and the parameter files in case an
error is made during the recovery
C). Correct the problem that caused the media failure.
If the
problem cannot be corrected, the
datafiles must be restored to an
alternate location. If this is the case, the ALTER TABLESPACE RENAME
DATAFILE command must be used to change
the location of the datafile in the control file .
D). If the
current control file do not match
the physical structure of the database at the time you want to recover to,
restore a backup of the control file that matches the database’s physical file structure at the point in time you want to recover to
replace all current control file of the
database with the one you want to use
for recovery. If you do not have a backup copy
of the control file you can
create new one,
E). Restore
backups of all data files. Make
sure the backups where taken before the point in time you are going
to recover to. Any data files added after the point in time
you are recovering should not
be restored. They will not be used in
the recovery and will have to be recreated after recovery is complete. Any data in the
datafiles created after
the point of recovery will be
lost.
F). Make sure
read-only tablespace are
offline before you start recovery so recovery does not try to update the datafile headers.
G). Start SQL*PLUS
and connect oracle as SYS
H). Start the
instance and mount the database
using STRARTUP command with the
MOUNT option.
I). If you restored
files to alternative location,
Change the location now in the control file by using the ALTER TABLESPACE
RENAME DATAFILE command.
J). Use the RECOVER DATABASE UNTIL CANCEL command to begin
cancel-based recovery. If a backup of the control file is being used, make sure
to specify the USING BACKUP parameter.
K). You can
check the ALERT file to see
if you incomplete recovery was actually
a complete recovery. If the recovery was a complete recovery the message in the ALERT file is as follows
L). RESETLOGS after complete recovery through change scn.
If the recovery was incomplete, the
following message is recored.
M). RESETLOGS after incomplete recovery UNTIL CHANGE scn
After opening
the database using the RESETLOGS option, perform a normal shutdown
and a full database backup. If you do not do this, any changes made after the
recovery and before the next full backup are unrecoverable . If you did
not reset the logs, the database is still
recoverable
After opening the database
using the RESETLOGS option, perform a normal shutdown
and a full database backup. If you do not do this, any changes made after the
recovery and before the next full backup are unrecoverable . If you did
not reset the logs, the database is still
recoverable.
52.Where
the RMAN store the data without the catalog?
CATALOG vs NOCATALOG the
difference in 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, controfile of target database is responsible.
53. How
to indentified the database(s) backed-up
by RMAN?
You don’t
have any view to identified
whether it is backed up or not.
The only option is connect
to the target database and give list backup, it will give us the
backup information with data and timing.
RMAN> Show all;
54. How
to indentified the expired, active, obsolete, backups? Which
RMAN command useful for us?
RMAN>crosscheck backup;
RMAN>crosscheck archivelog all;
RMAN>list backup;
RMAN>list
archive logall;
55.
How do delete old obsolete and expired
oracle RMAN backup?
If you unable to delete obsolete and expired oracle DB
backup from the catalog, it will cause some
unnecessary throw error message during backup and also it will take-up space at the file system level.
Also it is not recommended to directly remove the RMAN backup files from the file
system using linux rm command
The main parameter
that decides what to delete is the retention policy. To identify your retention policy connect using RMAN and
execute “show all” command
RMAN> show all;
CONFIGURE RETENTION POLICY TO RECOVERY WINDOW FO 4 DAYS;
56.
What is an obsolete backup?
Obsolete backup means the backup pieces is still
available but it is no longer needed, it depends on retention
57.How
to view the backups before delete
obsolete.
Before we delete, obsolete command it is always recommend
that the
RMAN cross check backup command will check the records to make sure the accurate
the record in the RMAN cataloag.
RMAN> CROSSCHECK BACKUP;
59.
How to view the backup after delete obsolete?
RMAN>LIST BACKUP SUMMARY;
60.
What is an expired backup?
Backup piece or backup set not found in the backup destination
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