Many IOS000I messages were issued during a CA DISK datasets' backup job (with the following format:
IOS000I C03D,F6,CMD,**,0E00,,80000000,GWK215,SGB07WRA, 091
Release : 12.5
Component : CA Disk Backup and Restore
this is a hardware error, not a CA DISK problem.
All volsers reporting IOS000I with CMD had files belonging to one certain application ' residing in the vicinity of Cylinder 8000.
There were several other files, residing on different DASD, that also had an embedded error within their records.
Deleting the files resolved the problem.