I was testing CF recovery, put a lot of messages to my structure, and backed it up and it looked like it had backed up no messages.
I got message CSQE121I MQPA CSQELBK1 Backup of structure APP1 completed at RBA=0201829487E2, size 0 MB.
This looked strange so I did it again and got
CSQE121I MQPA CSQELBK1 Backup of structure APP1 completed at RBA=02018353BACD, size 6 MB
The reason is that the BACKUP CFSTRUCT command does not backup the last nn seconds worth of messages. Messages older than this time are backup up.
So if you backup your CF structure are a significant workload - wait at least 30 second before issuing the backup command. This time period, the EXCLude INTerval (EXCLINT), on the BACKUP CFSTRUCT command is documented here.
For many people the structures are usually empty, or have messages only for a few seconds. So having this interval means you only backup the long lived messages, and so the backup usually contains no messages at all.
I put 10,000 1KB persistent messages to a queue, waited 30 seconds and backed it up.
The following messages were produced
00:00:00.00 CDL1 BACKUP CFSTRUCT(APP3)
00:00:00.00 CSQE105I CDL1 CSQELRBK BACKUP task initiated for structure APP3
00:00:00.00 CSQ9022I CDL1 CSQELRBK ' BACKUP CFSTRUCT' NORMAL COMPLETION
00:00:00.01 CSQE120I CDL1 CSQELBK1 Backup of structure APP3 started at RBA=00108B65BD44
00:00:00.85 CSQE121I CDL1 CSQELBK1 Backup of structure APP3 completed at RBA=00108CBAA5C8, size 20 MB
Backing up 10,000 1KB messages used 20MB and took 0.84 seconds
Backing up 10,000 10KB messages used 101MB and took 1.25 second.
Backing up 10,000 100KB messages used 986 MB and took 9 seconds
The queue manager used by the backup cfstruct command was doing no work so all the logging activity was due the backup cfstuct command. If the queue manager was processing application messages - or backing up multiple structures, the time to backup an individual structure will take longer. Backing up a CF structure can impact the online MQ transactions due to the increased logging activity, which may lead to an increase in commit time.