Transaction code RZ12 is used to define and maintain the RFC server groups parallel processed jobs. By default, a parallel-processed job uses all qualified servers in an SAP System according to automatic resource-allocation rules. However, by defining RFC groups, you can control which servers can be used for parallel-processed jobs. An RFC group specifies the set of allowed servers for a particular parallel-processed job. The parallel processing system has built-in safeguards that eliminate the possibility that a parallel job can soak up all of the resources in an SAP System and cause performance problems for other jobs or other users.
In addition to these built-in safeguards, you can optimize the sharing of resources through RFC server groups. In the context of parallel processing, a group specifies the set of SAP application servers that can be used for executing a particular program in parallel. The group used for a particular job step must be specified in the job-step program in the keyword CALL FUNCTION STARTING NEW TASK DESTINATION IN GROUP. You can also create your own more limited groups, view and maintain groups with transaction code RZ12.