Re: how can i increase rollback segments simultaneously??

On Wed, 30 Dec 1998 22:18:51 GMT, Jurij Modic <jmodic_at_src.si> wrote:
>On 30 Dec 1998 16:44:48 GMT, sweh_at_mpn.com (Stephen Harris) wrote:
>
>>Piotr Kolodziej (pkol_at_otago.gda.pl) wrote:
>>: Stephen Harris wrote in message <76bknd$12b$1_at_nebula.mpn.com>...
>>: >careful with thos though - if your database crashes while the largeroll is
>>: >online you may not be able to perform instance recovery properly...
>>
>>
>>: Why ? Could you tell us ...
>>
>>As I understand it (and I may be wrong....) this is because largeroll is
>>not listed in the init.ora file as being initially online, so the instance
>>recovery will be unable to find some of the rollback information required
>>to rollback incomplete transactions, after having replayed the redo logs.
>>
>>Simple fix is to add largeroll to the list of rollback segments in the
>>init.ora file, startup the database (which will now correctly perform
>>instance recovery), take the largeroll offline, shutdown the database
>>(cleanly!) and then remove largeroll from init.ora again.
>>
>>Note: this has only happened to me once before, so I may be wrong about
>>this :-)
>
>Indeed, I belive your assumption is not correct. I made some tests,
>aborting an instance with uncommited transactions in a rollback
>segment that is not automaticaly put online at database startup, but
>the instance recovery never failed.
>
>I belive Oracle temporaryly puts this "nonstandard" rollback segments
>online while performing instance recovery, if they contain any
>transactions that should be rolled back during instance recovery's
>rollback phase. After instance recovery is completed, those rollback
>segments are brought offline again.

According to Velpuri's backup book, this is almost correct. It says Oracle scans the undo$ table for the transaction tables, checks the transaction tables of rollback segments for uncommitted transactions, keeping all rollbacks acquired online, marking those with uncleanable transactions needs recovery, and leaving the others offline. I haven't played with this but I can imagine a number of situations that should be tried, particularly with a crash during a low point in activity in a configuration with numerous rollback segs - will there be an unexpected number of segments offline?

>
>>rgds
>>Stephen
>
>Regards,
>
>Jurij Modic <jmodic_at_src.si>
>Certified Oracle7 DBA (OCP)
>================================================
>The above opinions are mine and do not represent
>any official standpoints of my employer

jg
--
These opinions are my own.
http://ourworld.compuserve.com/homepages/joel_garry Remove nospam to reply. mailto:joel-garry_at_nospam.home.com Available for Oracle DBA work. Received on Thu Dec 31 1998 - 02:51:38 CST