The queue algorithm

When CICSPlex® SM uses the queue algorithm, if the transaction being routed has no active affinities, the load is distributed across a set of target regions. Selection criteria include the current task load, the health state, and the type of connection between the router and the target region.

If the transaction being routed has no active affinities, the queue algorithm causes CICSPlex SM to select the target region that conforms to the following set of criteria:
  • The region has the shortest queue of work waiting to be processed, relative to the maximum number of tasks permitted in the target region. This queue of work, also called the load count, is the count of all active and queued user tasks. By default, tasks queued for both MAXTASKS and TRANCLASS attributes are included in the load count. Use of the "Task load queue mode" attribute in the CSYSDEF resource table allows sites to exclude tasks queued for the TRANCLASS attribute from the load count. For more information about the "Task load queue mode" attribute in the CSYSDEF resource table, see CICS® system definitions - CSYSDEF.
  • The region is the least affected by conditions such as short-on-storage, SYSDUMP, and TRANDUMP.
  • The region is the least likely to cause the transaction to stop.
  • The region is the shortest path for interregion communication.
  • The region has a z/OS® WLM health value in the range 1-100.

The queue algorithm maximizes work throughput and standardizes response times across the CICSplex. This algorithm is very robust; it can accommodate differences in processor power, different maximum task values in the target regions, asymmetric target region configurations, and an unpredictable workload.