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Home -> Community -> Mailing Lists -> Oracle-L -> RE: log_file_sync io wait question
Have you played around with the size and number of your redo logs? Larger redo logs would mean fewer checkpoints.
Dropping redo log member mirrors is tempting, but RAID alone isn't enough protection. I experienced a corrupted file system one time, and I was glad that my redo logs were multiplexed on another file system.
>>> RMarkham_at_hafeleamericas.com 09/18/02 03:39PM >>>
well if you have mirrored members that exist on the same disk thats an
issue, if this same disk houses the currently used datafiles that would
add to the situation. I placed my redo on a seperate raid-1 and dropped
the member mirrors and see better stats. I have a buffer size 1mb but
I am using 11i applications. Also consider your log file
sizes, the larger the more it has to flush at a given time, but the
smaller the more often it has to flush.... all theses consideration above
need to be configured according to what you have available hardware-wise.
HTH
-----Original Message-----
Sent: Wednesday, September 18, 2002 1:09 PM
To: Multiple recipients of list ORACLE-L
We have a canned package that we use to insert approx 100 records/second
into one table (oltp environment).
Each record is just under 1K (datatypes = number and varchar).
There are several indexes that are build on the table as the records are
inserted.
Each and every record is committed.
Therefore we are flushing the 'redo log buffer' to disk (online redo
logfiles) 100 times per second (once per commit).
Not surprisingly we have noticed IO waits which we believe are associated with our 'Redo Log buffer'. Namely ;
log_file_sync = 180 waits/sec
log_file_parallel_write = 180 waits/sec
We tried resizing the 'redo log buffer' from 16K to 256K - but we did not
notice any improvements.
Neither Log switching or archiving seem to be excessive.
100 records per second seems to be our maximum speed without the application
queuing up and Oracle showing very high waits on log_file_sync and
log_file_parallel_writes.
Does anyone know how we might be able to minimize the IO waits?
Thanks in advance.
ENVIRONMENT
oracle : Oracle 8.1.7.4 os : Sun Sparc Solaris 8 box : 8x8 E10K IO : Hitachi SANS unit through fiber and Brocade switch _________________________
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