Switching from new function mode to compatibility mode on z/OS

The availability of new functions and backward migration for IBM MQ for z/OS® is controlled by the OPMODE parameter in the CSQ6SYSP macro. You should be aware of the implications of switching from new function mode to compatibility mode, that is, switching from OPMODE=(NEWFUNC,800) or OPMODE=(NEWFUNC,900) to OPMODE=(COMPAT,800) or OPMODE=(COMPAT,900).

Note: Backwards migration is not supported for a Continuous Delivery (CD) release. Queue managers running a CD release of IBM MQ must be started with OPMODE=(NEWFUNC,90x) where x is the modification level.

Switching from OPMODE=(NEWFUNC,800) or OPMODE=(NEWFUNC,900) to OPMODE=(COMPAT,800) or OPMODE=(COMPAT,900)

When you switch from OPMODE=(NEWFUNC,800) or OPMODE=(NEWFUNC,900) to OPMODE=(COMPAT,800) or OPMODE=(COMPAT,900), certain new Version 8.0 functions will no longer be available. This will cause the following conditions to occur:

• If the BSDS has been converted to version 2, the queue manager will not be able to access the BSDS when it is started in compatibility mode. This means that the queue manager fails to start and terminates with reason code 00D10120.
  • We can find the BSDS version by running the print log map utility (CSQJU004).
• Any buffer pools with an ID greater than 15 are marked as suspended. This means that these buffer pools cannot be used, deleted, or altered until the queue manager starts in new function mode again. Information about the buffer pools is kept in checkpoint log records until the queue manager starts in new function mode again.
  • Any page set that uses a suspended buffer pool is also suspended. Information about the suspended page set is also kept in checkpoint records.
  • While a page set is suspended, any messages in the page set are unavailable. An attempt to use a queue or topic which uses the suspended page set results in an MQRC_PAGESET_ERROR message.
  • While it is suspended, a page set can be associated with a different buffer pool by using the FORMAT function of the utility program CSQUTIL, specifying TYPE(REPLACE). We can then issue a DEFINE PSID command to bring the page set back into use with a different buffer pool.
  • Note: All units of recovery that involved the suspended page set, except units that are indoubt, will have been backed out by the queue manager when the page set was last used. Indoubt units of recovery can be resolved when the page set is again in use by the queue manager.
• Any buffer pools with an ID of 15 or less that have their LOCATION attribute set to ABOVE, have the LOCATION attribute switched to BELOW and their PAGECLAS attribute set to 4KB and the buffer pool size is set to 1000 pages.
• Any cluster-sender channels that have been configured to use a transmission queue other than SYSTEM.CLUSTER.TRANSMIT.QUEUE fail to start with message CSQX295E. To allow these channels to start, you need to perform the following actions:
  • Change the default cluster transmission queue configuration of the queue manager, so that all cluster-sender channels default to use the transmission queue SYSTEM.CLUSTER.TRANSMIT.QUEUE. We can do this by changing the value of the DEFCLXQ queue manager attribute to SCTQ.
  • Identify any manually defined transmission queues that have a non blank cluster channel name attribute value, by using the following command:

    DISPLAY QLOCAL(*) WHERE(CLCHNAME NE ' ')

    Change the cluster channel-name attribute value of these queues to blank.
• No inbound channels will be allowed to start if any channel authentication records have been created with a host name specified in their ADDRESS attribute. Message CSQY344E is issued for each channel authentication rule that uses restricted function, if this condition occurs.
• Defining channel authentication (CHLAUTH) with the CHKCLNT attribute, requires the queue manager to be running in NEWFUNC mode.

If you need assistance to revert to an earlier version of IBM MQ, contact your IBM support center.