Re: How to tune "redo log space request"?

Luca Minudel wrote:
>
> I've tried to increase log_buffer but nothing changed.
> I've tried to increase redo log files number but nothing changed.
> I've tried to increase redo log files size and I've got less frequent "redo log space requests" but the total "redo log space wait time" was quite the same.
>
> > You're always going to get some space waits during a log switch -
> You mean that it's not a performance problem having "redo log space requests"?
>
> > speeding up your log switches may be a better option...
> How can I do that?
>
> Thanks!
> ______________________________________
> Luca Minudel software designer
> Italy Conegliano (TV)
> e-mail luca.minudel_at_nline.it
> http://www.geocities.com/luca_minudel
>
> Connor McDonald <connor_mcdonald_at_yahoo.com> scritto nell'articolo <39F10997.7263_at_yahoo.com>...
> > Michael Bialik wrote:
> > >
> > > Hi.
> > > Try increasing log_buffer to 1048576 ( 1Mb ).
> > >
> > > HTH. Michael.
> > >
> > > In article <01c03ae1$35d9e960$239e15c2_at_w95luca>,
> > > "Luca Minudel" <luca.minudel_at_nline.it> wrote:
> > > > I've got a problem with an Oracle instance.
> > > > The instance has a "redo log space request" (and a consequent "redo log
> > > > space wait time") every time there is a redo log file switch.
> > > > The redo log files are huge (32MB) and are many (12 redo log groups of 1
> > > > file each). They are on 2 different fast disks/controllers/channels.
> > > > The log_buffer is set to 262144.
> > > >
> > > > As I know there should not be "redo log space requests". Isn't it?
> > > > How can I avoid them?
> > > > How can I find theyr cause?
> > > >
> > > >
> >
> > Whilst this lower the redo space statistics, it will probably increase
> > log file sync times as well as making the performance of the LGWR much
> > more sporadic...
> >
> > You're always going to get some space waits during a log switch -
> > speeding up your log switches may be a better option...
> >

If you have redo space requests that are NOT associated with log switches, then this can be considered a problem...

Some very simple things which will assist greatly are:

1. Separate your logfiles away from anything else - ideally each log file on a separate disk.
2. Make them raw

HTH

-- 
===========================================
Connor McDonald
http://www.oracledba.co.uk (mirrored at
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