> Tanel, > > Did you observe better performance? By how much? Do please let us > know!
Oracle Apps upgrade between major releases involves running hundreds of thousands scripts in bigger cases. Some of there scripts execute bigger transactions, but majority execute lots of small transactions and DDLs (even commenting on tables). And their script template has an additional commit in end of every script (in later db versions it is not that big problem in IO sense, because no commit really executed if no transactions are started in session). So, when I ran about 30000 scripts in 8 hours before disabling wait for sync, then after setting it, the scripts ran in about 3-4 hours . I started searching for this kind of parameter when saw a lot of log file sync waits during upgrading. And all of this was even before than I discovered _disable_logging ;) > > 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. As you just wrote - this parameter affects (changes behaviour) of LGWR, other processes work as usual, they wake up when theyre posted. Tanel. > > 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. > > > > > > ----- Original Message ----- > > > To: "Multiple recipients of list ORACLE-L" <[EMAIL PROTECTED]> > > > Sent: Wednesday, November 19, 2003 11:20 PM > > > query > > > > > > > > > > Hi! > > > > > > > > I've sometimes used setting _wait_for_sync�lse during Apps > upgrade > > > > projects, to upgrade performance. (As long as your database > doesn't > > > crash > > > > during the parameter is set to false, no problems should occur). > > > > > > > > I just started wondering, what would be the case if a parallel > query > > > starts > > > > during someone is modifying data... > > > > > > > > As I understand, when doing parallel query: > > > > 1) the dirty blocks which are supposed to be read by PQ in > direct > > > mode, > > > are > > > > flushed to disk > > > > 2) PQ reads the blocks in direct mode > > > > > > > > But when _wait_for_sync is set, the writes get acknowledged > > > immediately > > > (or > > > > acknowledgement is not waited for). Could this result in the > > > unlikely > > > > situation, that PQ issues the flush command to dirty buffers and > > > starts to > > > > read them, but actually reads the old images of the blocks, > since it > > > thinks > > > > the write has already occurred? > > > > > > > > (actually, this doesn't touch only PQ, it's possible to have > direct > > > reads > > > to > > > > PGA in serial mode too...) > > > > > > > > Tanel > > __________________________________ > 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). > >
