The archive or backup or ixmaint should be stopped during the REORG process ?
All update activity to the FILES data sets (FDS) should be stopped during the time they are doing the reorganization. The unload reads every record in the FDS and then writes it to a flat file. Next is to run a reload which reads the files from the unloaded flat file and inserts them back into a reinitialized FDS.
In the time between the unload and the reload the activity should be stopped that occurs against the FDS because if any new records are inserted then those could be lost during the reload because those new records would not exist on the unloaded flat file.