You most likely didn't completely "quiesce" your system prior to running the backup of library QUSRSYS and so there were still locks on objects in that library.
Quiesce is a French word. In the context of an iSeries backup, it means, "to bring the system to a quite state". One in which there is very little activity occurring on the system. This is not the same as a "restrictive state", which as you know, is required for a SAVSYS process.
There is a very important difference between quiesced and restrictive states. If you don't take the system down to a restrictive state, you can still run a backup process as an unattended batch job. (Note: In V5R3 BRMS allows you to submit a batch job to the controlling subsystem even in a restrictive state.)
Prior to starting my unattended SWA backup process, I end the following subsystems:
QINTER, QSPL, QHTTPSVR, QSNADS, QSVCDRCTR, QSERVER and QUSRWRK.
I also end the Mail Server Framework via the ENDMSF command.
I'm now in a "quiesced state".... Note, my backup process is still running in the QBATCH subsystem.
In my opinion, it is very important that you have journaling active for any backup/recovery process, too. If you don't, you can never recover any changes made between backups. However, it isn't a requirement of SWA if you "quiesce" the system prior to starting the backup. Once a synchronization point has been established by the SWA process, you can resume normal system operations. If you had to use these backup tapes to recover from a disaster though, you would only be able to recover to the time of the SWA synchronization. If you had journaling active you would be able to recover to the point of your last journal receiver backup.
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