Re: Backing Up Rollback Tablespaces

In article <1993Dec1.165956.25720_at_exlog.com> lparsons_at_exlog.com (Lee Parsons) writes:
>In article <1993Nov30.152606.3441_at_newsgate.sps.mot.com> kramer_at_ash.sps.mot.com writes:
>>If you never change the definitions you're probably OK.
>>But once I tried restoring an entire DB minus rollbacks
>>(expecting to use the ones currently defined) and it didn't
>>work (support got me up pretty quickly but it was definitely
>>a pain).
>
>But she said that this system was being backed up HOT. I don't think
>she could make this work because in order to bring up the DB
>she would have to define new RB Segments but the system wouldn't
>come up because archive logs would need to be applied.
>
>I'll have to test this for a definative answer but right now I
>suspect she would be hosed.

Ok after a quick test I found that this infact does work if you treat the RollBack Segment tablespace as if it where damaged or missing. I just marked it as offline and continued with the recover.

After that I could drop the old rollback segments and created a new tablespace and RBS.

The only thing I'm still not sure about is what whould have happened if the database had needed a large RBS inorder to apply the archive logs. My test db was very small so the SYSTEM tablespace must have been suffecient.

But what would have happened if some of my logfiles included the load of a 100m file?

The question then is: Does the Database use rollback segments during an online recover of the database?

The only reasonable answer is Yes. The implication is that not backing up the Rollback Segment Datafiles during a Hot backup is a gamble that when you recover you won't need them. Sounds more than a little scary to me.

Also from this I gather that it is ok to skip the backup of the RBS on a SHUTDOWN database provided you are willing (and able) to go throught the trouble of recreating them when you restore.

Comments?

-- 
Regards, 

Lee E. Parsons                  		Baker Hughes Inteq, Inc
Oracle Database Administrator 			lparsons_at_exlog.com