Back around Feb, 2001, IBM issued a series of informational APARs that
described a wide range of tuning recommendations. APAR PQ31226 contained
the following:
BLKSIZE
Specifies the block size of the archive log data set.
The block size you specify must be compatible with the
device type you specify in the UNIT parameter.
The parameter must be in the range 4 097 through 28 672.
The value you specify is rounded up to a multiple
of 4 096.
The default is 20 480.
This parameter is ignored for data sets that are managed
by the storage management subsystem (SMS).
If the archive log data set is written to DASD, you are
recommended to choose the maximum block size that will
allow 2 blocks per track. For example, for a 3390
device, you should use a block size of 24 576.
It would have been nice if IBM (also) provided the info as a SupportPac.
Jan van Kemenade
jvkemenade@CRES To: [EMAIL PROTECTED]
SIDA.INFO cc:
Sent by: Subject: Archive log block size
MQSeries List
MQSERIES@AKH-Wi
en.AC.AT
12/03/2002 04:43
AM
Please respond
to MQSeries List
Hi,
For those who still believe in 'tuning'...
The default blocksize for Archive logs is 20480 (5*4096).
No doubt chosen by IBM because this represents halftrack blocking on a
3380 disk (with lrecl=4096). But since 3390's have a larger track size,
an optimum blocksize would be 24576(6*4096).
Saves about 1/6 of the allocated archive log
Cheers, Jan.
-/
/Jan van Kemenade
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