IBM Professional Series User Manual page 352

NOP (X'03') and TIC (X'08') CCW codes are also
supported anywhere within the chain.
The condition and completion code are as follows:
CC=O
I/O complete with no errors
CC=1
Device availability error, reg 15 contains completion
code:
R 15 = 1 - Device not in virtual machine configuration
R15=2 - Device not available (e.g. disabled or powered
off)
R 15 = 3 - Attempt to write to read/only device.
R15=5 - Device busy
CC=2
CCW or control data error, reg 15 contains completion
code:
R 15 = 1 - extent error
R15=2 - operation error (operation byte in blockid
doesn't match the READ or WRITE CCW)
R15=3 - invalid CCW chain format
R15=5 - CCW string not on double-word boundary
CC=3
Unrecoverable I/O error, reg 15 contains completion
code:
R15=3 - CCW count not multiple of 512
R15=4 - End-of-File
R15=5 - Media I/O error
Appendix A. CP / CMS Interface A-13