Implement the larger log Relative Byte Address

Before Version 8.0, IBM MQ for z/OS used a 6 byte log RBA to identify the location of data within the log. From IBM MQ Version 8.0, the log RBA can be 8 bytes long, increasing the period of time before you have to reset the log.

This new feature needs to be explicitly enabled. See Plan to increase the maximum addressable log range for considerations when planning to enable 8 byte log RBA.

Important: If your queue manager is not part of a queue sharing group and you subsequently migrate back to Version 9.0.0, having enabled 8 byte log RBA, ensure that we are using OPMODE=NEWFUNC,900 at those releases, otherwise your queue manager will fail to start. Perform these instructions, in the order shown, to enable 8 byte log RBA on a single IBM MQ for z/OS queue manager:

1. If your queue manager is in a queue sharing group ensure that all queue managers in the queue sharing group that are at Version 9.0.0 are running with OPMODE=(NEWFUNC,900) before moving to step 2.

   You do not need to take a total queue sharing group outage to do this. We can stop each queue manager that is at Version 9.0.0 in turn, change it to OPMODE=(NEWFUNC,900) and restart it.

   Once all Version 9.0.0 queue managers in the queue sharing group are running with OPMODE=(NEWFUNC,900), perform the following steps for each queue manager in the queue sharing group until all queue managers are running with the new BSDS.

2. Allocate new BSDS data sets with similar attributes to the current BSDS. We can tailor sample CSQ4BSDS and delete any irrelevant statement, or we can use your existing JCL, but change the BSDS name to something like ++HLQ++.NEW.BSDS01. Notes:
   1. Check the attributes of our new BSDS before submitting the job to allocate the new BSDS. The only attribute that might change is the size of the BSDS.
   2. The new BSDS contains more data that the current BSDS, therefore, we must ensure that the new data sets are allocated with sufficient available space. The sample JCL in thlqual.SCSQPROC(CSQ4BSDS) contains the recommended values when defining a new BSDS.

3. Shut down the queue manager cleanly.
4. Run the BSDS conversion utility (CSQJUCNV) to convert the existing BSDS to the new BSDS data sets. This usually takes a few seconds to run.

   Your existing BSDS will not be changed during this process, and we can use that for the initialization of the queue manager in the case of an unsuccessful conversion.

5. Rename the current BSDS to become the old BSDS, and the new BSDS to become the current BSDS, so that the new data sets are used when you next restart the queue manager. We can use the DFSMS Access Method Services ALTER command, for example:

   ALTER '++HLQ++.BSDS01' NEWNAME('++HLQ++.OLD.BSDS01')
   ALTER '++HLQ++.NEW.BSDS01' NEWNAME('++HLQ++.BSDS01')
   

   Ensure that you also issue commands to rename both the data and index portions of the VSAM cluster.
6. Restart the queue manager. It should start in the same amount of time as it would have done when using 6 byte log RBA.

   If the queue manager does not restart successfully due to a failure to access the converted BSDS, attempt to identify the cause of the failure, resolve the problem and retry the operation. If required, contact the IBM support center for assistance.

   If necessary, the change can be backed out at this point by:
   1. Renaming the current BSDS to become the new BSDS.
   2. Renaming the old BSDS to become the current BSDS.
   3. Restarting the queue manager.

   Once the queue manager has been successfully restarted with the converted BSDS, do not attempt to start the queue manager using the old BSDS.

7. Message CSQJ034I is issued during queue manager initialization to indicate the end of the log RBA for the queue manager as configured. Confirm that the end of the log RBA range displayed is FFFFFFFFFFFFFFFF. This indicates that 8 byte log RBA is in use.

Note: In order to enable an 8 byte log RBA on a new queue manager, before it is first started, we must first create an empty version 1 format BSDS and use that as input to the BSDS conversion utility to produce a version 2 format BSDS. See Create the bootstrap and log data sets for information on how you carry out this process. Parent topic: Manage the logs

Related information

• Plan to increase the maximum addressable log range
• Larger log Relative Byte Address
• The BSDS conversion utility (CSQJUCNV)