John,

Rules of thumb work great 80% of the time.  ;-) From my experience I use
70% with a low secondary value and 60% when there is a high secondary
value.  I have seen cases (in Ecometry sites) where even 50% did not
reduce the secondaries.

If secondaries exists, look at the maximum number of contiguous blocks.
This determines the "pattern" of the secondaries, a high number of
contiguous blocks (* blocking factor) is called clustering.

Secondaries are caused by IMAGE key items hashing to the same record
location.  To determine how many secondaries are being generated there
are several tools.

DBGeneral
Adager includes a HOWMESSY.LIBRARY.REGO
LUND includes a DBLOADNG.UTIL.LPS

And it is also available from the Contributed Software library.

I like and use both DBGeneral and Adager.  DBGeneral can determine
optimum Master capacities through a technique called sampling. This is
good when Masters and Autos are small.

Adager has a GREAT undocumented feature to resolve clustering issues.

/Plug

Come to my talk at the Solutions Symposium and I will cover all of these
issues.  /End Plug

Regards,

Craig M. Lalley

Systems Performance Specialist
Lund Performance Solutions
Phone (541) 812-7600 | Email [log in to unmask]

Fax (425) 920-4995| Web www.lund.com

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-----Original Message-----
From: HP-3000 Systems Discussion [mailto:[log in to unmask]] On
Behalf Of John Penney
Sent: Thursday, March 28, 2002 5:35 PM
To: [log in to unmask]
Subject: [HP3000-L] Image D/B capacities

OK, 3000-L or those of you still with me at this hour:

I seem to remember from a '79 D/B course that there was a percentage, 70
or 75% above which you would experience degraded if not
molasses-in-February performance, if you didn't adjust the dataset
capacities.

Anybody can quote the source for this quotation?

TIA



John M Penney
Systems Programmer
Production Services
Information Services Department
Pierce County
Tacoma, WA
253-798-6215
253-798-6680 Fax
[log in to unmask]
www.co.pierce.wa.us

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