Re: ReDo Log Advice from ixora web site

Giganews Newsgroups
Subject: Re: ReDo Log Advice from ixora web site
Posted by:  Niall Litchfield (n-litchfie…
Date: Fri, 23 Apr 2004

"Charles" <cdavis107…> wrote in message
> the ixora web site give this advice about keeping ReDo log files open.
> Do the experts in this group generally concur with this advice?
> Charles
> Copy/Paste from ixora web site:
> Holding the log files open
> The greatest potential for tuning the speed of a log switch is in the
> opening of the new log file members. The operating system's open()
> system call is much faster if another process already has an open file
> descriptor on the same file. This is partly because certain
> information about the file is already cached in kernel memory. But
> more importantly in the case of raw logical volumes, it avoids a delay
> while logical volume state data reflecting the opening of the raw
> logical volume is written to the volume group reserved area on disk.
> The APT script is intended to be run daily from cron
> under Unix to hold all the log files for an instance open for the next
> 24 hours. The first time we tried this technique, it shaved an
> impressive 6 seconds of the speed of each log switch. Your mileage
> will vary depending on your logical volume or file system and kernel
> configuration, but it is sure to help a little.

Like Joel I'm hesitant to disagree with Steve but I would note a couple of

1. The script and associated question were written in the 7.3/8.0 timeframe.
Perfomance of checkpointing and log switches has improved since then.
2. How often do you log switch? The 'conventional wisdom' seems to suggest
that about every 15 minutes would be a 'good' frequency. Is saving 6 seconds
every 15 minutes going to make a significant difference?
3. Do a sanity check on the 6 second figure. Do you actually get that

Niall Litchfield
Oracle DBA
Audit Commission UK


In response to

ReDo Log Advice from ixora web site posted by Charles on 22 Apr 2004