RE: ALTER TABLE performance issues

Thanks, I should have mentioned that the only things happening on the system was the upgrade, this was being done during a dedicated upgrade period.

And the CPU load was only about 40%. This low level of CPU usage is another reason we thought there must be some way to improve this.

-----Original Message-----
From: midrange-l-bounces@xxxxxxxxxxxx [mailto:midrange-l-bounces@xxxxxxxxxxxx] On Behalf Of Alan Campin
Sent: Monday, November 15, 2010 3:05 PM
To: Midrange Systems Technical Discussion
Subject: Re: ALTER TABLE performance issues

Could be locks. If they are soft locks, it may take some time to end them.

Could be system load too.

On Mon, Nov 15, 2010 at 3:44 PM, Kruse, Kat <kkruse@xxxxxxxxxxxx> wrote:

Our developers have finally started using ALTER TABLE instead of
rename/copy method of changing files. One of the things we noticed is that
there are times that there are significant differences in the performance of
the change.

We've already suggested to them that instead of multiple passes with only
one change at a time, they should be doing all the changes in a single pass.
We've also noted where the differences can be accounted for by files with
many/few columns and by files with many/few rows.

After taking the above into consideration we're still finding that the
ALTER TABLE give very inconsistent results. For example, for a given file
which had 0 records, in library A it took 5 seconds to finish while in
library B (also 0 records) it to 22 seconds to finish.

FWIW, we're at V6R1 on Power7.

So, has anyone got suggestions at what we can look at or do to improve our
performance?

Thanks,
Kat Kruse
Qualcomm, Inc.
Systems Support Engineer

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