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SysAdmin's have a definate love/hate relationship with RMAN. Many of us
not so jokingly refer to it as the "Recovery Mangler". You love it because
its fairly simple and is the only sure-fire way to perform online backups.
You hate it because it's often cryptic, and either works or doesn't. Because
RMAN couples closely with a backup infastructure there is alot of finger pointing
when problems arise between "It's an RMAN issue!" and "No, it's a NetBackup issue!".
RMAN causes DBAs and UNIX admins to get too close for comfort and niether generally
understands the wholistic view of the interaction properly.
So, why would a sysadmin like RMAN?
- RMAN can perform online (hot) backups
- RMAN can allow for partial or complete recovery
- No fear of incomplete backups
- DBA initiated backups and recovery without the interaction of the SA
- Intigration with existing backup infistructure
The problem with backing up Oracle using traditional methods is similar to
the problems with backing up filesystems, unless you shutdown the database
and perform a cold backup there is no way to know that all the transactions
and changes have been written to datafiles. The SGA maintans a huge amount
of data in active memory which can cause a problem. It's alittle like
editing a configuration file on the system and then halting the system and
wondering where your changes went. In order to ensure consistance of the
database we need a hot backup method. If we restore a filesystem backup of
the database that was taken while Oracle was running we run the risk of lossing
database changes at best or having a corrupt database at worst.
Subsections
Next: Enabling ARCHIVELOG Mode
Up: The Cuddletech SAs Guide
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2005-02-10