Performance capacity for high availability

You should consider the capacity of the RDQM high availability (HA) configuration when planning for performance.

As a general rule, you should plan on an absolute maximum of 30 to 40 queue managers in an RDQM HA configuration. Be aware that if you approach this top limit, then it can take five minutes or more to restore the availability of all queue managers in the event of a failover. Too many RDQM HA queue managers also affects the performance of non-RDQM HA queue managers.

If you have more than the recommended maximum number of queue managers, as well as excessive switchover times, you might observe unwanted failed actions that require manual intervention. Note the following points:
  • The more RDQM HA queue managers you have, the more likely you are to experience failed actions.
  • Failed actions are most likely to occur in RDQM HA switchover events, but can occur in steady state operations too.
  • With very large numbers of RDQM HA queue managers, some failed actions might require assistance from IBM® Support to recover.

Expect worse performance in terms of failover times and failed actions as the messaging load increases.

Once configured, you should test your system in both of the following conditions with your anticipated workload:
  1. A planned switchover, where you suspend an RDQM HA queue manager.
  2. An unplanned failure (for example, loss of power or loss of network). Loss of communication causes the RDQM HA queue managers to be started on another node.