Recommended VDWQT / DWQT values

Brian Picard

Recommended VDWQT / DWQT values
Hello,
What should be the recommended values for a Buffer pool dedicated for those
objects that have a very frequent mass DELETE, INSERT, UPDATE, SELECT
actions within the same program?.
At the start of the program these objects are deleted and records get added
to the table later. Then several updates and reads happen on this table.
Can this be treated in the same way as SORT POOLS, basically high value for
deferred writes?.
If the value is too high, then at checkpoint, there would be too many pages
to be written. This will result in an elongated checkpoint queue. At this
time, if the program requests these pages that are already in the check
point queue, would there be a Async write-wait time?
So what value is ideal. Lower or higher?.
Regards,
Brian



Joel Goldstein

Re: Recommended VDWQT / DWQT values
(in response to Brian Picard)
Brian,
There is guideline number. You have to monitor your system/pools and
figure it out.

If the avg pages/write is a low single digit number, then vdwqt should be
zero

Sort pools are totally different. If most of the sorts can complete in the
pool, then raising vdwqt can save you some writes,
but make no difference for reads since they're in the pool.
However, raising the thresholds, when bigger sorts hit, will often cause
you to slam into spth, dmth, iwth because
the dasd subsystem can't complete the srites fast enough.

It's the standard tuning/balancing game and your system is different from
everyone else's.

Regards,
Joel


Message text written by DB2 Data Base Discussion List
>What should be the recommended values for a Buffer pool dedicated for
those
objects that have a very frequent mass DELETE, INSERT, UPDATE, SELECT
actions within the same program?.
At the start of the program these objects are deleted and records get added
to the table later. Then several updates and reads happen on this table.
Can this be treated in the same way as SORT POOLS, basically high value for
deferred writes?.
If the value is too high, then at checkpoint, there would be too many pages
to be written. This will result in an elongated checkpoint queue. At this
time, if the program requests these pages that are already in the check
point queue, would there be a Async write-wait time?
So what value is ideal. Lower or higher?.
Regards,
Brian
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