Maximum uncommitted messages (MAXUMSGS)

The Q replication and Event Publishing programs put and get messages from queues within a synch point, so the MAXUMSGS parameter might be a factor in your IBM® MQ tuning. MAXUMSGS is a queue manager parameter that limits the number of messages that can be put on queues or retrieved from queues within a synch point.

The Q Capture program puts messages on send queues and then commits them at an interval that you specify in the commit_interval parameter. The Q Apply program commits the messages that it deletes from the receive queue within an MQ unit of work.

The number of allowed uncommitted messages should be greater than or equal to the sum of the message limit (MAXDEPTH) of all queues that are defined within the queue manager. If you expect very large or long-running transactions in your environment, set this parameter higher than the default of 10000 messages. The maximum setting is 999999999 messages. If you reduce the default MAXUMSGS value, ensure that the new value is large enough to handle your peak replication workload.