What is the relationship between batch and dialog instances in SAP

[former_member84834]

Another Basis admin told me today that every batch job consumes at least one dialog instance and that you must always have at least one dialog process for every batch process. I always thought these were separate and unique processes and they was no relationship between the two. Which is true?

[Matt_Fraser · Accepted solution]

Timothy,

It's not a hard-and-fast rule, but it's a best practice recommendation. Many times a job running in a batch process may not need any additional work processes, but frequently batch processes will temporarily spawn other processes. This could be for generation of a needed program, for instance, or because the batch process is capable of running multi-threaded. When this happens, these child processes always occur as dialog (DIA) processes, not BTC processes.

So, the general recommendation is to have at least one DIA process on the instance for every BTC process. Furthermore, it's not a bad idea to have one DIA process for each of all other kinds of BTC processes; in other words, DIA processes should generally make up at least half of all the processes on the instance.

For an example of this in action that you can see for yourself, try running SGEN on a test server. While it's running, observe the processes in SM50. Typically, you'll see the one BTC process running the main program for SGEN, and anywhere from one to eight (or more -- this is configurable) DIA processes doing the actual program generation.

Cheers,
Matt

[former_member84834]

Thanks - I understand the various processes in SAP. I want to know if there is a one-to-one relationship between the dialog processes and the batch processes. For every batch process does the system require a dialog processes. In your screen shot you have 3 batch and 10 dialog. Could you have 10 batch and 3 dialog? Do batch processes require a dialog instance to get work done - or - does can a batch process perform work without using a dialog instance?

[Matt_Fraser]

Frank will not be notified of this reply unless you create it as a comment directly under his answer, i.e. click Comment on this answer instead of creating a new answer, just as I have done here.

[architectSAP]

Hello Timothy,

Both Dialog (DIA) as well as Background / Batch (BTC) are so called Work Processes (and there are further types as well, e.g. Update, Spool, Enqueue, etc.). Go to transaction SM50 to display the Work Processes in your system:

Best regards

Frank