Re: oracle redo log transaction

"orauser" <test_at_test.fr> a écrit dans le message de news:cn21vi$3rj$1_at_aphrodite.grec.isp.9tel.net...
> hi,
> i've read the guides from oracle but don't understand fully how redo logs
> works exactly.
> i'm coming from sqlserver world and i know i can't make a comparaison but
> ...
>
> I know that when a redolog is full, the LGWR do a log switch but what
> occrurs when a log are switched ?
> LGWR call DBWR to applies change from the current redolog (which will be
> switched) to the datafiles or/and the rollback segment ?
> then DBWR notifes LGWR that it can resume ?
>
> Now after the second log switch the first redo log will be rewritten and if
> i issue a rollback, from
> where the data are taken to rollback? from the rollback segment ?
> what process write to the rollback segment ?
> And if the DB crash, since the statement is not finished there will be a
> rollback ?
>
> why from a performance view, no one recommend a important redolog size ? >
> 50 Mo and onl 3 to 5 files ?
>
>
> Let's take a update statement on a big table (10 millions rows), if i have
> only 2 redo logs about 10 Mo each.
> How oracle does not return an error that redolog is full (like in mssql) ?
> is this the size of the rollback segment who actually limit the size of the
> transaction ?
>
>
> thx
> tom (apologies for my english)
>
>

Maybe you have to first read the first chapter of Concepts : Introduction to Oracle Server: http://download-west.oracle.com/docs/cd/B10501_01/server.920/a96524/c01_02intro.htm#20385

And maybe the whole book is useful.

-- 
Regards
Michel Cadot