Post queues' status from MTP displays high age minute value (4335471)

When operating Shareplex in MTP mode, the post queues' status displays the age with a high minute value.

While in STP the read release interval is checked against all the messages read by post, in MTP it is checked per subqueue. That is, only when the number of messages read from a subqueue reaches the read release interval will the subqueue be read released. If clients have set their read release interval fairly high in STP for performance, they should set it much lower for MTP.

The symptom of having messages in the queue and no backlog will not go away no matter how low the read-release interval is set. However, the higher the read-release interval then the greater the number of messages in the queue when backlog is zero.

We recommend setting the read-release interval lower because with MTP its effect has changed.

In general, the read release interval is set higher when data throughput is high in order to reduce the amount of time post spends check pointing to disk. The advantage of a high read-release interval is that post will process faster. The disadvantage is that when post exists abnormally, post must spend much more time reading through data that it has already processed before it can start processing the new data in the queue.

With MTP, since the read-release interval is being applied to each subqueue individually, the effect of setting the read-release interval to a high value is exaggerated.

If the read release interval was set to 10000 when the customer was using STP, and if with 5.3 the number of sessions at one time is, say 20, then each subqueue is only read released when the number messages read reaches 10000. If post cores instead of exiting normally, then there could be at most 20*9999 messages in each subqueue that must be re-processed by poster before it can begin processing new data.

Set SP_OPO_READRELEASE_INTERVAL to an appropriated value which may be smaller than the default value, and also set SP_OPO_IDLE_LOGOUT to small value than the current default value.