It depends on how many concurrent users you have for the device and the
pattern of usage, but unless you have a very unusual environment,
without PAV you will have a number of drives that regularly have I/O
that encounter queueing delays waiting for access to the UCB, and these
will see significant benefit from aliases. If you have a mix of short
transfers and very large transfers (e.g., DB2 tables), even one alias
can make a incredible difference on the consistency of short transfer
response times. You will see a lesser improvement with increasing
number of aliases until you reach enough so that no concurrent user for
the device ever has to queue for access to a UCB address. Depending on
your environment, even as low as 3 - 5 aliases for a 3390-3 may be
adequate to give outstanding performance. In other environments, it may
make more sense to let WLM handle PAV assignments.
McNeely, Tu wrote:
I would like to know if there are any significant improvement in
performance when using PAV?
And in your experience, how many aliases does it take per CU/device to
make a substantial difference?
...
--
Joel C. Ewing, Fort Smith, AR [EMAIL PROTECTED]
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