Planning to increase the maximum addressable log range

You 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 8.0 , see Larger log Relative Byte Address.

If the queue manager is not in a queue-sharing group, you can upgrade the queue manager to IBM MQ 8.0 , enable Version 8.0 new functions, and convert it to use 8 byte log RBA values at any time. Once a queue manager has been converted to use 8 byte log RBA values, it is not possible to revert it to COMPAT mode.

For queue managers in a queue-sharing group, you can upgrade each queue manager in turn to IBM MQ 8.0 and enable Version 8.0 new function. Once all the queue managers in the group are at IBM MQ 8.0 new function mode, you can 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.

Note: A queue manager that has been converted to use 8 byte log RBA values can read logs that have data written with 6 byte or 8 byte log RBA values. Therefore, its active logs and archive logs can be used to recover page sets and coupling facility (CF) structures.

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.

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.