Maximum number of dialog work process

[Former Member]

Hello gurus,

Could you please let me know what is the maximum number of dialog work process that you can configure in an Netweaver system with ABAP 7.0 before considering to install a new application server to distribute the load?

Thaks for your help,

Best regards

[Former Member · Accepted solution]

Max Work Process number (DIABTC...) = 99 in RZ10,

but when you edit instance profile parameter rdisp/wp_no_dia= XXX desired value but you cannot control this using RZ10 also SAP will not support this.

Thanks

SM

[Former Member · Accepted solution]

Thanks for the informatoin SM,

Do you know what metric or parmeters can you take into account to verify if additional processes can be added? I know HW resources are related with the maximum number of WP that can be configured but I would like to know what do I need to check in specific?

Best regards

[markus_doehr2 · Accepted solution]

> Do you know what metric or parmeters can you take into account to verify if additional processes can be added? I know HW resources are related with the maximum number of WP that can be configured but I would like to know what do I need to check in specific?

The workprocess itself uses only, if started, a small amount of memory, it attaches to the shared memory segments that hold all the data. So that memory is not the issue.

There are, however, other things to consider:

- database connections/processes (can the databse configured to offer additional client processes?)

- IPC shared memory parameters (depending on what OS you use)

- operating system shell limits (on *nix operating systems)

I wouldn't configure such a huge amount of WPs. If you consider, that if only 1/4 of those are active you'd need roughly 25 CPUs to handle that load and context switches et al. I'd install a new application server to handle the load instead of increasing WPs more if there are already a lot.

Markus

[Former Member · Accepted solution]

Thank you very much for the clarification Markus,

Just one question, according to the following statement, can I think that I should estimate a usage of 1/4 CPU core by every dialog WP?

"If you consider, that if only 1/4 of those are active you'd need roughly 25 CPUs to handle that load and context switches et al..."

Do you know any SAP note that could help me to estimate the number of WP according to the load of the system?

Kind regards,

Rodolfo

[markus_doehr2 · Accepted solution]

> Just one question, according to the following statement, can I think that I should estimate a usage of 1/4 CPU core by every dialog WP?

No, this was just an example to make clear what I mean.

> Do you know any SAP note that could help me to estimate the number of WP according to the load of the system?

There is no such note and there can't be.

You could have a system with e. g. 100 users where 10 of them do really produce load, the other 90 may just run a few transactions or do just nothing - so 50 WPs is too much. You could also have a system with 20 users where ALL are entering data all data and doing reporting and stuff so 20 WPs is too less. There may also be processes like ATP that use one background worprocess and spawn a number of dialog WPs you configure in the application. If you configure too few of them, the ATP run will run very log, if you configure too much, the system will be overloaded and slowing down. I can imagine dozens of other examples what may cause load or not.

Because of that it's not possible to give a formular how many WPs to be configured for how many users.

This is a tuning thing and needs to be estimated in the first weeks after a GoLive; watch the system, reconfigure, watch. Check ST03N and SM50/SM66 or book an early watch after some time, they have rough estimates and give usually good advises. Out of theory it's almost impossible to predict something.

Markus

[Former Member · Accepted solution]

Thanks for the information Markus, I appreciate the help provided.

Best regards

[Former Member]

Rule of thumb - 5 to 10 WPs per processor.

Logic: You would not want to spend more than 20% of your response time in CPU.

Response time is broken down into waiting time for a resource (in this case CPU) and the actual service time. If you see a steady numbers of more than 2 requests per processor core, that would mean your CPU is not able to service the request immediately and there is a subsequent wait time in the overall response time. In that case you will want to reduce the number of WP that will in turn reduce the wait time.

Regards,

-sushil