Channel auto-definition exit program

The channel auto-definition exit can be used when a request is received to start a receiver or server-connection channel but no definition for that channel exists (not for IBM MQ for z/OS ). It can also be called on all platforms for cluster-sender and cluster-receiver channels to allow definition modification for an instance of the channel.

The channel auto-definition exit can be called on all platforms except z/OS when a request is received to start a receiver or server-connection channel but no channel definition exists. We can use it to modify the supplied default definition for an automatically defined receiver or server-connection channel, SYSTEM.AUTO.RECEIVER, or SYSTEM.AUTO.SVRCON. See Preparing channels for a description of how channel definitions can be created automatically.

The channel auto-definition exit can also be called when a request is received to start a cluster-sender channel. It can be called for cluster-sender and cluster-receiver channels to allow definition modification for this instance of the channel. In this case, the exit also applies to IBM MQ for z/OS. A common use of the channel auto-definition exit is to change the names of message exits (MSGEXIT, RCVEXIT, SCYEXIT, and SENDEXIT) because exit names have different formats on different platforms. If no channel auto-definition exit is specified, the default behavior on z/OS is to examine a distributed exit name of the form [path]/libraryname(function) and take up to eight chars of function, if present, or libraryname. On z/OS, a channel auto-definition exit program must alter the fields addressed by MsgExitPtr, MsgUserDataPtr, SendExitPtr, SendUserDataPtr, ReceiveExitPtr, and ReceiveUserDataPtr, rather than the MsgExit, MsgUserData, SendExit, SendUserData, ReceiveExit and ReceiveUserData fields themselves.

For more information, see Work with auto-defined channels.

MQ_CHANNEL_AUTO_DEF_EXIT (ChannelExitParms, ChannelDefinition)

ChannelExitParms are described in MQCXP. ChannelDefinition is described in MQCD.

MQCD contains the values that are used in the default channel definition if they are not altered by the exit. The exit can modify only a subset of the fields; see MQ_CHANNEL_AUTO_DEF_EXIT. However, attempting to change other fields does not cause an error.

The channel auto-definition exit returns a response of either MQXCC_OK or MQXCC_SUPPRESS_FUNCTION. If neither of these responses is returned, the MCA continues processing as though MQXCC_SUPPRESS_FUNCTION were returned. That is, the auto-definition is abandoned, no new channel definition is created, and the channel cannot start.