Relation nr of DIA WPs to CPU usage

[jo_degraeve]

Hello group

The last weeks, by reducing our nr of WPs week by week by 1, we'r trying to determine how many DIAs we need for our current user population (900 users).

We have now come to the bottom line I think, because in rare cases we start getting Wait times. We have dropped to 18 DIAs (coming from 27) and think we will be OK at 20 DIAs.

Now, my real question : in reducing the nr of DIAs, we had presumed that the AVG CPU usage on the system would drop. However, on the contrary, we notice that actually CPU usage has increased ???!! Also Pool swaps seem to increase.

Is there any logical explanation to this ? Is it due to the fact that DIA processes need to be rolled out/rolled in more frequently ?

Jo

[Former Member]

Hi Jo,

I do have never seen this and cannot explain it either - I'm sure, it has nothing to do with each other !

20 sounds good to me in your case, but if you want to increase to 27 again, I don't see, that CPU shrinks down AND performance stays the same ...

If the CPU dropps down again, you just overload the server and therefore the performance is worse and you just see less CPU because of that ...

Regards

Volker Gueldenpfennig, consolut international ag

http://www.consolut.de - http://www.4soi.de - http://www.easymarketplace.de

[Former Member]

Hi Jo,

This is interesting, and we have done the opposite by increasing the WPs at times until now we have over 35. Our user population is similar, split over three shifts.

I think swapping and WP usage depends a great deal on the type of programs being run. I monitor sm50 and have a view defined that floats to the top any active work process. Many times a single user will run a program such as a settlement job that suddenly shows up on 5 dialog WPs. This type of event can eat up WPs very fast and slows things down considerably. I would rather have extra WPs and use some temporary memory than squeeze the users.

But I am interested in seeing greater CPU usage since it never goes very high on our system. We also have 5 each of update-1 and update-2 WPs, again because some of our programs seem to use the update-2 type more than you would expect.

The best thing is to have lots of main memory unless you are fortunate to have many processors.

So I would agree that the CPU is busy moving user context in and out and that would lead to swapping as well.

Regards,

Pat