Re: ROLLBACK segments' size: what criteria to size them ?

monsri_at_my-deja.com wrote:

> Hi,
> I'd just like to know how you DBA's managed to choose
> your rollback segments size when you created your
> database(s)...
>
> Could you please gimme some advice about this issue ?
> You size your rbs depending on what in particular ? Is
> there a formula perhaps (kind of "# of users expected
> x size of tables + # of DML statements..." etc etc.) ??

There are probably any number of formulas that can be used to calculate the size. They may work for you and they may not.

The general rule of thumb that I use is that if log file switches are occurring more than once every five minutes under the average load then the log files are probably too small. On the other hand, if there are no log file changes in a twenty-four hour period and transactions are occurring during that time then the log files are probably way to large. I try to shoot for a time between 5 and 30 minutes for log file switches under average load conditions. This means that under heavy load they will occur faster and under light load they will occur less frequently. Received on Fri Nov 24 2000 - 19:53:03 CST