Re: waits on only one rollback segment

joani_tamminen_at_yahoo.com (Joani Tamminen) wrote in message news:<11f13276.0206051241.66efbb90_at_posting.google.com>...
> We find the following problem on one of our production databases. This
> is my colleague's description about the problem: We are running Oracle
> 8.l.7.0 on AIX 4.3.3
>
> ------------------------------------------------------------
> We have a database with 4 rollback segments. Each rollback segment is
> on each separate rollback tablespace. Each rollback tablespace size
> 1500M. During monitoring, I saw many waits on one of the rollback
> segments rbs2.
>
> Then I added two more rollback segments in a new rollback tablespace -
> each of them about 650M.
>
> I still see lots of waits - the strange thing is the waits are only
> one rollback segment rbs2. I do not see any waits on any of the other
> rollback segments. I looked at the v$waitstat table for "undo header"
> before and after adding the new rbs segments and I see almost the same
> number of waits.
>
> I am watching the waits every hour and find that waits on rbs2 is
> usually 1938 or 1939 while all the other rbs (rbs1, rbs3, rbs4, rbs5,
> rbs6) are close to 0.
>
> My question is: why are waits happening only on rbs2? What am I doing
> wrong?

It's possible that the work of the database is directed into this specific rollback segment (using 'set transaction use rbs...').

To check if this is the case, make this RBS offline and see if you get errors...

Regards,
Boaz.

>
> ----------------------------------------------------------------------------
Received on Sun Jun 09 2002 - 12:30:08 CEST