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June 18, 2008
RMAN Studies Begin
This week I began my in depth studies of the Oracle backup and recovery manager (RMAN). The UCS department purchased a great reference book on RMAN and I've begun reading it. Yes, it is a rather dry subject, but this book is a wealth of information. Here are some things I've learned so far:
- RMAN is installed as part of the Enterprise database, it exists in every db we have.
- RMAN connects internally to the db as sysdba.
- The control file contains information about all data files (.dbf) and RMAN stores backup information about each data file right in the control file. This is why it is not good to lose all copies of your control file.
- RMAN copies data files at the block level. No other backup strategy can do this. This results in a lot of benefits such as the ability to delete "null" blocks and blocks containing no data during backup.
- RMAN can backup the db while it's running (hot) without interfering with the use of the db. It does this by cloning the control file and making a backup consistent with the cloned control file. The db continues to work using the real control file.
- RMAN copies the blocks directly into one big file, in chunks, often using more than one process, and only RMAN can ever get them back to their rightful places again.
There's more, but you can get the idea of the types of things that I'm learning about RMAN. I still need to learn about coordinating our RMAN backups (all db's have current RMAN backups) with a good tape backup strategy, then deleting unnecessary backups. Also, the interaction between RMAN and the Flashback area needs more study.
Oh, by the way, the db's are running strong. I managed to screw up the Helpdesk app a little doing some tuning on it, but other than that I've kept under the radar.
Posted by rossm at June 18, 2008 9:28 AM
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