The foreground process is affected. Instead of waiting for the LGWR, it will return right away.
Anjo. ----- Original Message ----- To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]> Sent: Thursday, November 20, 2003 4:24 PM in parallel > :) > > I admit, that I don't know either, which processes are affected by this parameter. > If foreground ones are, that should mean that after posting lgwr, they won't wait on semaphore and continue their work. > > If it affects lgwr, it means that lgwr posts the waiting processes immediately "back" before writing to disk. > > I'm too lazy now, but it can probably be figured out by tracing semop() syscalls... or maybe Steve Adams happens to read this post :) > > About "scientific" test results, the results I posted earlier, they were done exactly on same hardware, with same dataset and from same starting point. Enough scientific for me. > > Tanel. > > > I think my understanding was wrong. _wait_for_sync actually only > > changes the > > behavior of foreground processes. When set to false, they don't wait > > for > > LGWR > > to write redo records to disk; instead they continue to do their work > > as if > > log > > file sync already finished. It *does not* change any behavior of LGWR, > > notification or not. Correct me if I'm wrong again. > > > > I'm still interested in Tanel's benchmark, though. Only that is > > scientific. > > > > Yong Huang > > > > --- Yong Huang <[EMAIL PROTECTED]>, i.e. myself, wrote a few minutes > > ago: > > > Tanel, > > > > > > Did you observe better performance? By how much? Do please let us > > know! > > > > > > From what I read, _wait_for_sync when set to false means LGWR > > immediately > > > notifies user (foreground) processes that redo record writes are > > done > > (even > > > though they're not). When you say the parameter only affects LGWR, > > you > > need > > > to > > > clarify what you mean by "affect"; it changes the notification > > (posting) > > > behavior of LGWR therefore changes the behavior of waiting processes > > (*when* > > > they stop waiting). Just semantics. > > > > > > Yong Huang > > > > > > --- Tanel Poder <[EMAIL PROTECTED]> wrote: > > > > Anjo, > > > > > > > > I also thought it affects only lgwr sync, but Jonathan Lewis once > > told > > that > > > > it affects any disk writes... > > > > > > > > If it affects only lgwr, then great, I can make Apps upgrades, > > which do > > > > really lots of DDLs and small transactions, quite much faster that > > way... > > > > > > > > Thank you, > > > > Tanel. > > > > > > > > > > > > > _wait_for_sync basically meant that a session is waiting for > > the sync > > > > > of the > > > > > redo by the lgwr. Normally the redo log writer writes to disk > > and then > > > > > notifies the session that the transaction is completed. By > > setting > > > > > this to > > > > > false, you no longer wait for the redo to go to disk. > > > > > > > > > > That has no impact on your situation. > > > > > > > > > > Anjo. > > > > > > __________________________________ > > Do you Yahoo!? > > Free Pop-Up Blocker - Get it now > > http://companion.yahoo.com/ > > -- > > Please see the official ORACLE-L FAQ: http://www.orafaq.net > > -- > > Author: Yong Huang > > INET: [EMAIL PROTECTED] > > > > Fat City Network Services -- 858-538-5051 http://www.fatcity.com > > San Diego, California -- Mailing list and web hosting services > > --------------------------------------------------------------------- > > To REMOVE yourself from this mailing list, send an E-Mail message > > to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in > > the message BODY, include a line containing: UNSUB ORACLE-L > > (or the name of mailing list you want to be removed from). You may > > also send the HELP command for other information (like subscribing). > > > > > -- Please see the official ORACLE-L FAQ: http://www.orafaq.net -- Author: Anjo Kolk INET: [EMAIL PROTECTED] Fat City Network Services -- 858-538-5051 http://www.fatcity.com San Diego, California -- Mailing list and web hosting services --------------------------------------------------------------------- To REMOVE yourself from this mailing list, send an E-Mail message to: [EMAIL PROTECTED] (note EXACT spelling of 'ListGuru') and in the message BODY, include a line containing: UNSUB ORACLE-L (or the name of mailing list you want to be removed from). You may also send the HELP command for other information (like subscribing).
