IBM MQ for z/OS considerations for extended transactional client connections

Some XA transaction managers use sequences of transaction coordination calls which are incompatible with the features normally available to clients connecting to IBM MQ for z/OS®.

Where an incompatible sequence is detected, IBM MQ for z/OS might issue an abend for the connection and return an error response to the client.

For example, xa_prepare receives abend 5C6-00D4007D, with return code -3 (XAER_RMERR) returned to the client.

For transaction managers which encounter this situation, take the following actions to allow the transaction manager to interact with IBM MQ for z/OS:

• Apply the fix for APAR PI73140.
• Enable the change provided by PI73140 for the server-connection channel used by the transaction manager.

  You enable the change by specifying the keyword CSQSERVICE1 (in upper case) anywhere in the description field of the SVRCONN channel.

Note that channels with the CSQSERVICE1 keyword have the following restrictions:

• GROUP unit of recovery disposition is not permitted. Only QMGR unit of recovery disposition is allowed.

  An xa_open call specifying the queue sharing group name in the xa_info parameter fails with xaer_inval.

• The MQGMO_LOCK and MQGMO_UNLOCK options are not permitted. An MQGET call with MQGMO_LOCK or MQGMO_UNLOCK fails with MQRC_ENVIRONMENT_ERROR.