Thanks... good info... On Mon, 12 Nov 2001 06:45:21 -0800, you wrote:
>Generally I try monitor v$filestat to see what >proportion of IO is due to rollback...The ideal is of >course nil, but to do so pretty much means giving >everyone a couple of dozen 1555's every day :-) > >So you end up with the balancing act of trying to make >them as small as possible without introducing 1555's > >hth >connor > > --- Doug C <[EMAIL PROTECTED]> wrote: > Thanks.. makes >sense... >> Can I use x$bh or something to determine whether >> it's nicely squeezed into the >> buffer at some point in time? >> >> >> On Mon, 12 Nov 2001 02:00:21 -0800, you wrote: >> >> >If rb's are small, then there is a good chance that >> >just when they are about to aged out of the buffer >> >cache, hey presto! another session needs them again >> - >> >so you end up with a nice scenario where they spend >> >their life in the cache and cause virtually no IO. >> > >> >As they get larger and larger, the >> time-before-reuse >> >time gets longer and longer - which will mean more >> and >> >more IO. Its the same for having lots of extents - >> >many moons ago this used to be due to txns needing >> >their own extents. Oracle lifted this restriction >> >somewhere in v7, but it still makes sense to have >> 20 >> >or so extents, because then when a rollback segment >> >increases in size, it does it in nice 5% increments >> - >> >keeping the probability of it all fitting in the >> cache >> >high. >> > >> >hth >> >connor >> > >> > --- Doug C <[EMAIL PROTECTED]> wrote: > OK.. this >> may >> >be a little naive..and maybe I'm just >> >> jogging my own memory, but >> >> here it goes... >> >> There are a couple schools of thought on rollback >> >> segments as near as I can >> >> figure. Some like to set optimal, and some >> don't. >> >> The one's that don't like >> >> to shrink them at night or once daily or some >> other >> >> variation.. >> >> >> >> Question: Why bother? If they get big and you >> have >> >> the room, so what? They >> >> won't have to extend tomorrow, no? If you're >> >> concerned about space, why not set >> >> a good maxextents or a limit on the filesize.. >> >> >> >> What's the problem with them getting large? >> >> >> >> Thanks, >> >> Doug >> >> >> >> >> >> >> >> >> >> -- >> >> Please see the official ORACLE-L FAQ: >> >> http://www.orafaq.com >> >> -- >> >> Author: Doug C >> >> INET: [EMAIL PROTECTED] >> >> >> >> Fat City Network Services -- (858) 538-5051 >> FAX: >> >> (858) 538-5051 >> >> San Diego, California -- Public Internet >> >> access / Mailing Lists >> >> >> >>-------------------------------------------------------------------- >> >> 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). >> > >> >===== >> >Connor McDonald >> >http://www.oracledba.co.uk (mirrored at >> >http://www.oradba.freeserve.co.uk) >> > >> >"Some days you're the pigeon, some days you're the >> statue" >> > >> >__________________________________________________ >> >Do You Yahoo!? >> >Everything you'll ever need on one web page from >> News and Sport to Email and Music Charts >> >http://uk.my.yahoo.com >> >-- >> >Please see the official ORACLE-L FAQ: >> http://www.orafaq.com >> >> -- >> Please see the official ORACLE-L FAQ: >> http://www.orafaq.com >> -- >> Author: Doug C >> INET: [EMAIL PROTECTED] >> >> Fat City Network Services -- (858) 538-5051 FAX: >> (858) 538-5051 >> San Diego, California -- Public Internet >> access / Mailing Lists >> >-------------------------------------------------------------------- >> 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). > >===== >Connor McDonald >http://www.oracledba.co.uk (mirrored at >http://www.oradba.freeserve.co.uk) > >"Some days you're the pigeon, some days you're the statue" > >__________________________________________________ >Do You Yahoo!? >Everything you'll ever need on one web page from News and Sport to Email and Music >Charts >http://uk.my.yahoo.com >-- >Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Please see the official ORACLE-L FAQ: http://www.orafaq.com -- Author: Doug C INET: [EMAIL PROTECTED] Fat City Network Services -- (858) 538-5051 FAX: (858) 538-5051 San Diego, California -- Public Internet access / Mailing Lists -------------------------------------------------------------------- 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).
