Showing posts with label Oracle database 11g RMAN. Show all posts
Showing posts with label Oracle database 11g RMAN. Show all posts

Sunday, June 14, 2009

Can you make something too simple?

I'm working on the new revised edition of our Oracle Database Backup and Recovery book for Oracle Database 11g ... I've been looking at some comments here and there that have been made about the book, and also comments about the competition. What I find interesting is that the approach that the competition has taken, the recipe approach if you will, seems to be popular with some. I suppose that makes sense. Everyone wants something to be easy. But that's the rub, can you take something as complex as backup and recovery and make it too simple?

In the recipe book, in the first two chapters they have you do a backup recipe and a restore recipe. Now the Junior DBA (or perhaps the overworked senior DBA) might say, FANTASTIC, I backed up my database and I restored my database, I'm set. They might just setup a script, start backups and off they go, not fully realizing what they have just done.

For in the book, they fail to mention some salient points.

1. That the recipe will have you backing up into ORACLE_HOME by default. Since there is no previous recipe to configure the Flash Recovery Area, that is where your backups will go by default.

2. They do have a recipe for putting the database in ARCHIVELOG mode... However if you do that first and then follow the recipe for backing up your database, you might find yourself in a world of hurt. The backup recipe does not backup archived redo logs.

3. Since you are not backing them the archived redo logs, or removing them, guess what happens to the archive log destination directory?

So in an effort for simplicity the chapter falls short of the mark a bit. I know we all want simple solutions. Something we can craft out of the box without having to understand, without having to think, and that's all well and good. I'm not sure it's practical when dealing with backups of your database.

I'd love your feedback on how we can make our RMAN book better. I'd love to hear any suggestions you might have out there on how we can make it better, what we can add, modify or even delete.

Saturday, October 11, 2008

The dangers or RMAN Autocataloging...

In later versions of RMAN (at least 11g) when you perform certain types of database recoveries and duplications RMAN will catalog the backups for you. This is handy if you have a newly recovered control file, since it will get all of the archived redo logs and backup sets cataloged for you.

I do a lot of RMAN testing where I create databases, drop them, re-create them, recover them, etc... I've noticed that this can have some odd impacts sometimes if you have old backups or archived redo logs from a previous version of that database. Say, for example you create an ORCL database, do a lot of stuff with it, delete it and create a new ORCL database. Sometimes RMAN will get weirded out when it tries to catalog the old backups or old archived redo logs.

I have not taken the time to try to figure out all the dynamics on what is going on here but I would recommend that anytime you remove a database and intend to re-create it, that you move the backups and old archived redo logs out of the FRA or the archivelog destination directories somewhere else if you need to keep them. This will make your RMAN life much easier.
 
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