The round-robin algorithm

The round-robin algorithm assumes that all server groups are equally valid for selection.

In the round-robin algorithm, when the Client daemon is initially started, it reads from the configuration file a list of all possible server groups to which any ECI or EPI request can be sent.

The Workload Manager also records the last server group selected. When a new ECI or EPI request is made, the next server group in the list is selected as the target. When it reaches the last server group it loops around to the first one.

Examples

For each of these examples, assume that workload management is set up with the example configuration described in Information required by Workload Manager, and that workload management is enabled for all programs and server groups.
  • The first request sent for the program PROG2 goes to GROUP1, the second request for PROG2 goes to GROUP3, the third to GROUP1 again, and so on.
  • All requests to PROG3 go to GROUP2.
  • Half of the requests to PROG2 go to GROUP3, and all of these requests go to CICS6 because this is the only server in GROUP3.

Thus, the first request for PROG2 is sent to GROUP1, and a server from GROUP1 is selected at random. For example, CICS2 might be selected. The second request for PROG2 is sent to GROUP3, and CICS6 is selected because it is the only server in GROUP3. The third request for PROG2 is sent to GROUP1 again, and CICS2 is selected because it was the first server selected in GROUP1.