questions about order for using extended memory and heap memory

[wa13n]

hi,all

as i read sap abap performance analysis, they say work processes(WPs) first use the extended memory(Xmem) in shared memory(Smem), then if it become out of extended memory, WPs use heap memory.

why does WPs use Xmem first? there should be reason for this...

[dasistdochscheisse]

That's only true for dialog work processes. These are shared among all users and for this reason the user data needs to be shared among all dialog processes (your next diualog step can be performed by a different WP than the one before). And only EM can do that. Once the quota is reached, a dia process uses heap memory and becomes PRIV, which means, the process is exclusively used by one user.

If all dia processes are PRIV, this can be compared with a system stand still for all other users. So you do not want too many dia processes to go PRIV and there a profile parameters to deal with this.

Batch jobs occupy a batch work process until the job is finished, there is no need to share the context of the WP with oder processes. And for this reason, batch processes use heap memory first and once the limit is reached they use EM, too.

With report RSMEMORY you can see the actual limits and change them online.

[mercedes_fernandez · Accepted solution]

Hello Yuki,

Extended memory is shared by all the work process, that makes possible that the different dialog steps of an SAP transaction can be executed by different work process and only get occupied during the time the dialog step takes.

When the work process starts using heap (private) memory the work process keeps occupied with the same transaction, doesn't get release between dialog steps.
This local memory only gets released when the work process is re-started

kind regards,
Mercedes