Re: How to manage rolback segments?

Hi John,

Thank you for all of your precious input and sorry for the mismatched information, in fact I had one configuration when I sent the first message and changed when I sent the second.

I'm now trying to configure a pool of 8 rollback segments in a tablespace ROLLBACK_DATA. The tablespace is now 2GB and each rollback segment has the following settings:

MINEXTENTS: 2
MAXEXTENTS: 2000
INITIAL: 200K
NEXT: 200K
OPTIMAL: 20M However, I'm still getting messages of "cannot extend rollback, snapshot too old, segment too small". As far as I noticed, select statements are generating rollback segments, and I supposed only INSERTs, UPDATEs and DELETEs did so.

Our queries act on large selections, sometimes more than 8 million records at a time. Shoud I have rollback segments as large as the database?

Even a single SELECT COUNT(ROWID) FROM TABLE is generating a rollback error. Is it because the table is too large?

Any suggestions would be very appreciated.

On Mon, 05 Apr 1999 20:56:15 -0500, John Higgins <JH33378_at_deere.com> wrote:

>Maybe I don't get it or maybe you made a typo, but:
>If the 5 rollback segments are only 20 MB then they have not yet grown as
>big as the 50 MB OPTIMAL.
>
>If you meant that the OPTIMAL is 50 K, then here is an answer: you have set
>MINEXTENTS to 2, so each rollback segment must have a 10 K initial extent
>and a 300 K next extent. At some time after a transaction caused a rollback
>to extend, it would have had the 10K initial extent and some number of 300K
>extents. When the shrink occurs, it cannot go below 2 MINEXTENTS. In
>addition, it is possible that the 10K extent is among those given back --
>then the MINEXTENTS=2 would mean 2 extents of 300K.
>
>HTH
EBR
** Please remove the primes to get my real e-mail Received on Tue Apr 06 1999 - 19:42:38 CDT