Plan to increase the maximum addressable log range

We can increase the maximum addressable log range by configuring your queue manager to use a larger log relative byte address (RBA).

For an overview of the change to the log RBA for IBM MQ Version 8.0, see Larger log Relative Byte Address.

If the queue manager is not in a queue sharing group, we can convert it to use 8 byte log RBA values at any time. If you subsequently migrate back to Version 9.0.0, ensure that we are using OPMODE=NEWFUNC,900, otherwise the queue manager will not start.

Before any queue managers in a queue sharing group can be converted to use 8 byte log RBA, all queue managers in the queue sharing group must be at one of the following levels:

  • At Version 9.0.n CD, Version 9.1.0 LTS, or later
  • At Version 9.0.0 and have been started with OPMODE=(NEWFUNC,800), or OPMODE=(NEWFUNC,900)

We can then change each queue manager in turn to use 8 byte log RBA values. It is not essential to change all the queue managers at the same time.

When a queue manager in a queue sharing group has been converted to use 8 byte log RBA values, other queue managers in the queue sharing group can use the logs of the converted queue manager, even though they have not yet been converted to use 8 byte log RBA values. This is useful, for example, for peer recovery.


Undoing the change

The change cannot be backed out.


How long does it take?

The change requires a queue manager restart. Stop the queue manager, run the CSQJUCNV utility against the bootstrap data set (BSDS), or data sets, to create new data sets, rename these bootstrap data sets, and restart the queue manager. The CSQJUCNV utility usually takes a few seconds to run.


What impact does this have?

  • With 8 byte log RBA in use, every write of data to the log data sets has additional bytes. Therefore, for a workload consisting of persistent messages there is a small increase in the amount of data written to the logs.
  • Data written to a page set, or coupling facility (CF) structure, is not affected.

Parent topic: Plan your logging environment


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