Re: Space Contention and LOG_BUFFER size

More than the number of time you are waiting for 'redo log space requests' its more important to find out how long you are waiting for that. 27 times out of a million might not be a big deal for you to tune.

having said that, here is a posting by Steve Adams on this topic

"Q : Every day our production database has more than 10 redo log space requests. Oracle suggested that this number should be near 0.
I resized the log files, and increased the log buffer to 1M. What else can I do?

A : This idea of increasing the log_buffer to get space requests down to 0 is both ineffective and bad for performance. There is always a risk of space requests at log switches and a few other points when redo generation is disabled entirely.  It does not matter how big your log buffer is then. You will get space request waits if you try to generate redo at that time. Also, a large log buffer is actually much worse for performance than the occasional space request, even if that is a genuine log buffer space wait. "

hth

babu

"Farnsworth, Dave" <DFarnsworth_at_Ashleyfurniture.com>@fatcity.com on
07/30/2002 12:19:02 PM

Please respond to ORACLE-L_at_fatcity.com

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I am doing some performance monitoring on an 8.1.7 DB on Windoze. I ran the following query;

SQL> select name,value
  2 from v$sysstat
  3 where name = 'redo log space requests';

NAME                                                                  VALUE
---------------------------------------------------------------- ----------
redo log space requests                                                  27

If the number of 'redo log space requests' is much over zero then I should increase the LOG_BUFFER size in my init.ora, at least that is what I get from RTFM. One question I have is that does the size of the LOG_BUFFER parameter have to be a multiple of the DB_BLOCK_SIZE parameter? I vaguely remember that it shuold be but have not found anything in TFM to verify this.

Thanks,

Dave

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