rman recovery scenarios. 1) complete recovery 2) loss of system datafile 3) loss of non-system...
TRANSCRIPT
1) Complete Recovery
2) Loss of System datafile
3) Loss of Non-System datafile
4) Restoring a datafile if no backups
5) Restoring a tablespace
6) Loss of controlfiles
7) Loss of online redolog files
Agenda
Rman started from version 8
Rman backup is taken by oracle when dba submits it as a job
Rman backup does not backup by file(cb or hb or mirror image
backups).Rman backup is content backup
Rman backups those used blocks(not by entire file)
Rman offers two types of backups
1)Regular backup(used blocks)
2)Incremental backup(changed blocks)
Rman takes less time and backup space
We need not depend on writing batch files like shell scripts in
unix as Rman has its own scripting language which is platform
independent
INTRODUCTION TO RMAN
Rman is capable of cleanup of obsolete archivelogs at the end
of successful backup
From oracle 10g it started offering compressed backup(even
less time/space)
Rman can perform backup of multiple destinations parallel
At the end of successful Rman backup we can ask Rman to
check for the validity of the backup
Using Rman we can identify corrupted blocks and recover
them
We need not depend on o/s schedulars like cron in unix as it
has its own schedular
RESTORE AND RECOVERY CONCEPTS
We take the cold backup by shutting down the database
followed by backup of C/R/D files at o/s level
If the database is in NALM(No archive log mode) and in case
of database crash we can only go for simple restore(SR)
If the database is in ALM(Archive log mode) we have a choice
of 1)Simple Restore(SR)
2)Restore+Recovery(R+R)
Recoveries are of two types
1)Complete Recovery(CR)
2)Incomplete Recovery(ICR)
We use archive log files for recoveries
CR would be possible only if we have both
*Current control file
*Current online redolog file
If any of the above two files is missing then we endup
performing ICR
ICR can be done in following ways
*Until cancel
*Until time
*Until SCN
At the end of ICR
1) we must open the database with
resetlogs option 2)Immediately take one
consistent cold backup
CR can be done in 2 ways
*Online(If system dbf file is present)
*Offline(If system dbf file is unavailable)
Whenever we perform ICR by opening the database with
resetlogs option a new incarnation will be generated and all
the backups taken with previous incarnations with orphand
status will become invalid backups and they are not useful
for restoring the database
Vva
CONTROL FILE
FIXED AREA
ROTATION AREA
Db nameContains names and locations of datafiles and redolofilesTimestamp of db creationWhether the db is in noarchive or archivelog modeCheckpoint infoLog sequence numberLast backup information
Contains info of RMAN backups