How do you set up load balancing for updates (to exclude a server)?

[Former Member]

Hi

From time to time we need to exclude an application server (we have 15) from the load balancing groups so that it isn't used; sometimes this is because we need to restart it (but don't want to kill existing user/background sessions) or because it's being isolated for use by a project/interface etc.

We usually take the server out of the groups in SMLG (dialog), RZ12 (RFC) and SM61 'Job Servergruppen' (background processing using group SAP_DEFAULT_BTC).

However - we have occasionally seen 'new' (not old background jobs still running on there) processes on these app servers even though it's out of these groups.

I've done some digging and it looks like there's load balancing/distribution done for UPDATE processes too:

http://help.sap.com/saphelp_nw70ehp2/helpdata/en/00/93dc3017714c0b809c93562aff717c/content.htm

http://help.sap.com/saphelp_nw70ehp2/helpdata/en/84/674683da254bebb3f4c046be8d497a/content.htm

I've created a new group here in SM14 and assigned all the servers but one to test this.

The big question though is: How do you actually TELL the SAP system to USE this particular group?!?!

For the SMLG load balancing it's obviously users SAP GUIs/ TWS and other interfaces connection settings; for RZ12 / RFC balancing you set in SMQ* transactions, and the existence of SAP_DEFAULT_BTC in itself means that group is used for background processing. So how do you get SAP to use the new update group?

Also: am I missing something else, some other load distribution? I swear I've seen DIA and RFC processes on the damn application server too!!!

Thanks!

Ross

[moti_shakutai]

Hi,

You should look into the following parameters (at instance level rz11):

1) rdisp/vb_factor - if you set it to zero, then no update request will be sent over to this server. Usually you will use this parameter to increase the update load on a strong server with more resources.

2)rdisp/vb_dispatching

Moti

[Former Member]

Hi Ross,

Does some of the RFC and SAPGUI clients connect to the application server directly, instead of using logon load balancing.

Best regards,

Orkun Gedik

[Former Member]

Hi Orkun

No they shouldn't do, we may have one of two users/interfaces incorrectly going straight to the Central Instance, but not to a particular application server. I'm certain they are being load balanced by the system to this application server.

I've spoken to an ABAP expert and he says:

From an ABAP point of view, if a program spawns intra-system RFCs without using an RFC server group then the default is to use all available system resources regardless of them being defined in an RFC server group.

So if there's poor programming it sounds like it will just ignore the groups...

Regards

Ross