Re: How many rollback segments can a transaction use?

Comments inline.

"michael ngong" <mngong_at_yahoo.com> wrote in message news:ecf365d5.0307090520.ff449ae_at_posting.google.com...
> Oracle8(TM) Server Concepts "
>
> When a transaction runs out of space in the current extent and needs
> to continue writing, Oracle finds an available extent of the same
> rollback segment
> "
> This I intepret to mean if two transactions are running two rollback
> segments are to be used

No, they are using at most 2 rbs segments, maybe they share one.

>
> My version/OS Oracle 8i Hp Unix 9000.
> When I run a query for the number of transactions I get 2
> select current_utilizations from v$resource_limit where
> name='transactions'
>
> RESOURCE_NAME CURRENT_UTILIZATION
> ------------------------------ -------------------
> transactions 2
Ok, 2 running transactions at this very moment.

>
> When I find the change in writes after a period of say 10 minutes I
> expect may be two rollback segments to change since two transactions
> are active.From my understanding of the DOCS these two transactions
> should use two rollback segments.
> but five of my rollback segments indicate an increase in the amount of
> writes
> time:3:50a
>
> select n.name,writes from v$rollstat r,v$rollname n where n.usn=r.usn;
> SYSTEM 2580
> RBS1 101758434
> RBS2 241709876
> RBS3 31058582
> RBS4 37506164
> RBSBIG 62053292
> Time 4:10a
> select n.name,writes from v$rollstat r,v$rollname n where n.usn=r.usn;
> SYSTEM 2580
> RBS1 112648128
> RBS2 241712898
> RBS3 111247476
> RBS4 37512038
> RBSBIG 62058182
>
> I should be missing something and will greatly appreciate your insight
You are missing that in the meantime many other transactions were done (maybe by the same 2 sessions).

Regards Stephan Received on Wed Jul 09 2003 - 09:04:31 CDT