ca.portal.admin

Performance Degradation after Database Enlarge/Expand

Discussion created by ca.portal.admin on Feb 8, 2006
From: Bill Vohs, SC Data Center, Monroe, Wi
Date: February 1, 2006

Subject: Enlarge/Expand IDMS Database Causes Severe Performance
Degradation

We are running:

z/OS 1.4
IDMS Release 16 SP02
EMC DMX2000 DASD

We have a need to enlarge a number of the IDMS databases.

Every time we do, we experience severe performance degradation.
Run times elongate by a factor of 3 to 5.
Job that ran in 30 minutes now takes 3-4 hours.

Our first attempt was back in November 2005.
The approach at that time was to do an UNLOAD and RELOAD to the enlarged
area.
This time we enlarged the databases by a factor of 3.
I.e. One database went from 15,000 tracks to 45,000 tracks.
Another database went from 7,000 tracks to 21,000
tracks.
These all on 3390 DASD on the EMC DMX2000.

Our run times were:

Before UNLOAD/RELOAD 11/09/2005 74
minutes
11/10/2005 46 minutes

After UNLOAD/RELOAD 11/16/2005 174
minutes
11/1/2005 198 minutes

This happened with almost every one of our jobs.

Our second attempt was January 29, 2006..
The approach this time was to do a EXPAND PAGE to an enlarged area This
time the databases were enlarged by a factor of 2.
One database went from PAGE SIZE 5064 to 10796 from 15,000 tracks to
30,000 tracks.
Another database went from PAGE SIZE 5064 to 10796 from 7,000 tracks to
14,000 tracks.

The run times are:

Before EXPAND PAGE 01/26/2006
64
minutes

After EXPAND PAGE 01/31/2006
209
minutes
02/01/2006 212 minutes


We have had an IDMS consultant review our work and he says every thing
looks great.

Our z/OS and IDMS statistics show nothing out of the ordinary.

We are at a bit of a loss.

Might anybody have any suggestion for us?

"
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Re: Performance Degradation after Database Enlarge/Expand
"Bill,

Did you look at your clustering before you just increased the number of
pages in the areas? The unload/reload may not have been able to improve
the clustering without increasing the page size too.

If you are looking at an area by using an index that could find data
randomly in an area, then expanding the number of pages will increase
run times. Here an area sweep could be a better choice.

Did you change your buffering after the expand? Could you use memory
cache to hold data above the bar in your online?

Just a few questions to answer.

Chris Wood
Alberta Department of Energy
CANADA

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