Re: Buffered log Vs. Unbuffered Log Database
From: "Yuri Dovgart" <y_dovgart@tci.ukrtel.net> > >Unbuffered logging means, that logical log buffer will be flashed as soon, >as transaction commited. Buffered logging means, that buffer will be >flashed >when it's full. Unbuffered logging takes much log space but ensure that no >transaction will be lost. Buffered logging means faster writes to logical >logs but if you switch power off, with transactions in buffer, this >transactions will be lost. And how many committed transactions are there in the average 32K buffer? :-) ______________________________________________________ Get Your Private, Free Email at http://www.hotmail.com
I have found that people often see buffered and unbuffered logging as being associated with a database, while it is really associated with a user. The user assumes the buffered mode set by the database, but he/she may change it themselves. Many customer batch jobs can be re-executed if a failure occurs, so consider setting the logging mode of the batch programs to buffered logging, while leave the default mode set to unbuffered. This will reduce the I/O to the logical logs and allow the batch jobs to piggy back on the commits of the OLTP users. Oh yeh, how you change the buffer/unbuffered mode is by a simple SQL "Set" statement in the application. This has been documented since version 4.0, but I wonder how many people are taking advantage of this??? ---jmiller Obnoxio The Clown wrote: > From: "Yuri Dovgart" <y_dovgart@tci.ukrtel.net> > > > >Unbuffered logging means, that logical log buffer will be flashed as soon, > >as transaction commited. Buffered logging means, that buffer will be > >flashed > >when it's full. Unbuffered logging takes much log space but ensure that no > >transaction will be lost. Buffered logging means faster writes to logical > >logs but if you switch power off, with transactions in buffer, this > >transactions will be lost. > > And how many committed transactions are there in the average 32K buffer? :-) > > ______________________________________________________ > Get Your Private, Free Email at http://www.hotmail.com