Point to check Logon Load balancing is configured correctly in SAP ABAP system.
1) Check/verify count distribution through AL08 or AL08_OLD.
We can start transaction AL08_OLD or AL08 to get an overview of the distribution of your logged on users and how they are spread over the application servers, it will show data like no of active user application server wise which further distribute them in no of Interactive users ( login from GUI), Number of RFC user ( connection from RFC) and Number of Plugin Users ( HTTP connection user session).
2) Through SMLG setting:
In SMLG we can choose menu option Goto / Load distribution to get an overview of the current load distribution and quality. A higher quality number means it has the best quality. New users that logon will be routed to this server if we have set the SMLG settings to Best Quality.
As per the SAP Note:2244136 we can use the recommended setting for logon group in the details of each logon group we can make dedicated settings:
The Fav.Typ setting indicates the load balancing mechanism (round robing, best performance, weighted round robin). Set Ext RFC-enabled to also do load balancing in this group for external RFC calls.For higher Load system can use weighted round robin as per above SAP Note.
We can set limits per application server on response time and amount of users. This limit is not a hard limit, but a soft limit to influence the quality calculation. The setting is per application server and it is across the logon groups (we cannot make settings per logon group)as mentioned in SAP note 118093.
3) RFC load balancing:
In RFC SM59, there is option to use -Load balancing setting and respective setting details, as shown below.
4) RFC load balancing for external system to SAP through Jco Connection:
Many external systems connect to SAP via the SAP JCO connector. The JCO connector can do load balancing, if configured properly. SAP Note note 2508036 help to understand in details about this.
5) RZ12 RFC server group:
With transaction RZ12 we can setup RFC server groups that also can be used for load balancing purposes.
6) RFC load balancing for qRFC:
we can configure load balancing for qRFC through the RFC group (settings made in RZ12) in transactions SMQS and SMQR.
7) Web traffic load balancing:
For web traffic load balancing, we have to set up the SAP web dispatcher. In the SAP web dispatcher we can configure to which back-end application servers to use, if applicable.
8) Batch job load balancing:
Batch job load balancing can be done by setting up batch job server groups in transaction SM61, we an maintain load balancing for batch execution.
9) In SPRO:
In SPRO, we can configure specific load balancing for specific process like for eg. MRP run, is very important for business and through SPRO we can configure parallel processing as per requirement.
10) Check Program variant:
In many SAP program/report there is way to schedule/run in parallel processing, so make sure option correctly configured or mentioned in those Program Variant.