Configuring cluster channels for availability

Follow good configuration practices to keep cluster channels running smoothly if there are intermittent network stoppages.

Before you begin

Clusters relieve you of the need to define channels, but you still need to maintain them. The same channel technology is used for communication between queue managers in a cluster as is used in distributed queuing. To understand about cluster channels, you need to be familiar with matters such as:
  • How channels operate
  • How to find their status
  • How to use channel exits

About this task

You might want to give some special consideration to the following points:

Procedure

Consider the following points when configuring cluster channels
  • Choose values for HBINT or KAINT on cluster-sender channels and cluster-receiver channels that do not burden the network with lots of heartbeat or keep alive flows. An interval less than about 10 seconds gives false failures, if your network sometimes slows down and introduces delays of this length.
  • Set the BATCHHB value to reduce the window for causing a marooned message because it is indoubt on a failed channel. An indoubt batch on a failed channel is more likely to occur if the batch is given longer to fill. If the message traffic along the channel is sporadic with long periods of time between bursts of messages a failed batch is more likely.
  • A problem arises if the cluster-sender end of a channel fails and then tries to restart before the heartbeat or keep alive has detected the failure. The channel-sender restart is rejected if the cluster-receiver end of the channel has remained active. To avoid the failure, arrange for the cluster-receiver channel to be terminated and restarted when a cluster-sender channel attempts to restart.
    [z/OS]On IBM® MQ for z/OS®
    Control the problem of the cluster-receiver end of the channel remaining active using the ADOPTMCA and ADOPTCHK parameters on ALTER QMGR.
    [UNIX, Linux, Windows, IBM i]On Multiplatforms
    Control the problem of the cluster-receiver end of the channel remaining active using the AdoptNewMCA, AdoptNewMCATimeout, and AdoptNewMCACheck attributes in the qm.ini file or the Windows Registry.

Example

See Suggested settings for examples of how you implement these settings on both IBM MQ for z/OS and IBM MQ for Multiplatforms.