Using PREPARE MIGRATE

The PREPARE MIGRATE command completes the following tasks:

• Walks through the list of all queues within the queue manager that is currently selected by runnscnf.
• For each queue matching the pattern given in the PREPARE MIGRATE command, it calculates the attributes the queue file should have according to the runnscnf configuration. These parameters are:
  • Location (subvolume) for the queue file
  • Primary extent size
  • Secondary extent size
  • Number and location of partitions (if any)
  If there is a mismatch between the configured values and the real values (for example if the configuration was changed after the queue was created), the queue is put in the list of migration candidates.
• The list of migration candidates, together with information about the reason why this queue is a candidate, is displayed.

The PREPARE MIGRATE command does not change any persistent state in the system. Each new PREPARE MIGRATE command calculates everything from scratch. So, if the list printed by PREPARE MIGRATE has too many entries, or entries you do not want to migrate now, you can reissue the command using a different pattern so that the result set matches your expectations.

The runnscnf session remembers the result of the PREPARE MIGRATE command for a subsequent START MIGRATE command. START MIGRATE always works on the set of queues calculated by PREPARE MIGRATE. This separation of the PREPARE MIGRATE and START MIGRATE commands has the following advantages:

• Multiple migrations can be initiated and started in one step. If required, multiple queues can be migrated with just two commands.
• You can control of the number of migration processes running in parallel, so that the I/O load does not cause any system problems.