I remember a paper several years ago by Dave Merit, who, at the time, was at
Bradmark.  His studies showed, and were confirmed by others, that the
benefit of using a prime number wasn't that it was the best capacity,
rather, it was never the absolute worst in the range.  So, in the absence of
doing master set capacity sampling,
pick the prime.  Just keep in mind that if you desire better performance,
you will want to do some sampling.
Also keep in mind that sampling is generally slow and does take resources to
perform.
 
Another issue to keep in mind about secondaries is that they aren't
necessarily all that bad.  Secondaries which
occur within the block boundary take very little resources to recover.
Secondaries which reside outside block
boundaries *may* result in additional I/O, which, by definition, is bad.
Depending on how the I/O is performed,
multiple pages/blocks may be brought into memory when the original I/O is
performed.  Stan can give the rules
on how many pages are brought in for what type of I/O.
 
What I have been  seeing is that it really isn't worth a ton of labor to
address the master sets, just pick the best
number and move on.  Especially in a dynamic environment where master
capacities change a lot.
 
Just my $.02 worth.
 
Bill Lancaster
Lancaster Consulting
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Bill Lancaster         Lancaster Consulting
(541)926-1542 (phone)  (541)917-0807 (fax)
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