Pythian Blog: Technical Track

Survey Results: Why Do You Use RMAN Catalog DB for Your Oracle DB Backups?

by Yury Velikanov on Jul 8, 2012 12:00:00 AM

Backup is one of the most important topics for any Oracle DBA. It is our primary responsibility to make sure that at any point in time we can recover a database. This is why I can't stop thinking about this topic and hope to release more related blog posts in the near future. Some time ago, I created a survey (my very first one): " Why do you use RMAN catalog DB for your Oracle DB backups?" As I am unsure of whether or not we should use RMAN catalog database and what should be the important input information for a decision-taking process. In this blog post, I will share the survey's results. You can find my short comments on the results at the end of this blog post. Please feel free to leave your option in the comments sections. 1.Are you using RMAN catalog DB for your Oracle DB backups?
Answer Response Percent Response Count
I (organization I am working for) use RMAN for backing up Oracle DBs and USE catalog database 70.8% 17
I (organization I am working for) use RMAN for backing up Oracle DBs but I DON'T USE catalog database 25.0% 6
I (organization I am working for) DON'T USE RMAN for performing Oracle DBs backups (if yes don't answer rest of the questions) 4.2% 1
answered question 24
2.What was the primary purpose to build and use RMAN catalog in your organization?
Answer Response Percent Response Count
Additional control files' metadata backup 47.4% 9
Keep backup history longer than control file can keep it 47.4% 9
Centralized reporting purposes 36.8% 7
Primary & Standby databases backups synchronization 21.1% 4
Store backup scripts to be executed an several databases 21.1% 4
We don't use RMAN or RMAN Catalog 21.1% 4
answered question 19
skipped question 5
Other reasons Using a catalogue is a defined business standard.
Duplicates
Catalog backups stored using MML library
3.What REALLY you are using RMAN catalog database for?
Answer Response Percent Response Count
Centralized reporting purposes (please specify reports you are running on regular basis in other filed) 31.3% 5
Additional control files' metadata backup (please specify use cases from your experience) 31.3% 5
Keep backup history longer than control file can keep it (please specify use cases from your experience) 31.3% 5
Primary & Standby databases backups synchronization 25.0% 4
We don't use RMAN or RMAN Catalog 25.0% 4
Store backup scripts to be executed an several databases (please tick this option if you REALLY use RMAN scripts stored in the catalog) 12.5% 2
answered question 16
skipped question 8
Other reasons easy clone database
Ah well, I suspect the real reason is to keep controlfile sizes to a minimum and still have the ability to keep details about old(er) backups.
Report on databases needing backups and trends in backup timings and sizes for capacity planning. Cases where control_file_record_keep_time wasn't changed from default (7 days) and information about older backups needed.
* repository: we use hand made reports on RMAN repository e.g. to 'crosscheck' backup-pieces RMAN knows about with backup-pieces our Symantec NETBACKUP knows about. They are not 100% in sync all the time. Also APEX reports about backup quality per DB is in use. (management style reports) * RMAN repo is protected by DAtaGuard on 2nd location - therefore it's part of disaster recovery: RMAN repo protected by DG; backup pieces protected by NETBACKUP duplication to 'other side' * control file history: some backups are kept for 'history' snapshots - nothing to keep in controlfile
Duplicates
Catalog backups stored using MML library
Query RMAN catalog and report on the backup status of every database in the catalog. If you have more than one, this is very usefull

Yury's comments

I'm planning to continue blogging on the topic. And my working name for the next related blog post is "You probably don't need RMAN catalog database" where I am going to give more analysis. As of now, let me highlight some points:
        • One of the good reasons to have catalog I missed initial is "DUPLICATE ... FROM ACTIVE DATABASE". This option requires RMAN catalog database connection. (2012.07.10 Yury: I stand corrected. Please see comments. Thanks Mdinh and Anand.)
        • ~25% of the people who participated in the survey don't use RMAN catalog database.
        • It looks like some DBAs initially planned to use a catalog database for storing RMAN scripts. However, some of them didn't implement it.
        • Additional control files' metadata backup is one of the most popular reasons to use catalog database.
        • Other popular reasons are "keep backup history longer" and "centralized reporting purposes".
        • Some other interesting reasons to use catalog database are "defined business standard" and "catalog backups stored using MML library".
Feel free to comment, Yury

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