Definition of 0P18


Cause: Unit check (command reject). Invalid CCW command or command sequence was
detected, or
An attempt was made to write on a write—inhibited 2314 drive, or
An attempt was made to write Home Address with mask off on a 3330, 3333, or 3340, or
An invalid seek was attempted on a 3330 or a 3333.
Programmer Action: Check the command sequence in your source program. If it is correct,
obtain a system dump (supervisor and partitions) and check the operation codes in the CCW
string pointed to by bytes 8-11 of the CCB addressed in the message. Some probable errors
are write commands issued to a file-protected tape that is not at load point, a write to a DASD
device without a preceding search, or two successive reads without an intervening feed for a
Operator Action: See Figure 4 at the beginning of this section. Check, by issuing the LISTIO
command. that all assignments have been correctly made.
If the problem recurs, have the
· system dump (see DOS/VS SADP)
· job stream
· log sheet
· program listing
available for problem determination.

Used with Courtesy and Permission of International Business Machines, Inc.