451

Explanation
The error occurred during the processing of SETPRT.
 Either the DCB whose address was passed in the SETPRT parameter list
is incorrect, the DEB address located through the DCB was incorrect,
the DCB EXIT LIST address located through the DEB was incorrect, or
the IOBs located through the DCB are incorrect.
This system
completion code is accompanied by message IEC918I. Refer to the explanation
of message IEC918I for complete information about the task that was
ended and for an explanation of the return code in register 15.

System programmer response
  If the error recurs and the program
is not in error, look at the messages in the job log for more information.
Search problem reporting data bases for a fix for the problem. If
no fix exists, contact the IBM® Support
Center. Provide the JCL and the program listing for the job.

Programmer response
For return code 01, make sure that DCBEXLIST points to a valid
exit list in your region.
For return code 02, make sure that the DCB fields DCBIOBAD and
DCBIOBA have not been overlaid since the DCB was opened.  Make sure
that the IOB or ICB link fields have not been overlaid.
For return code 03, make sure that the DCB field DCBDEBAD has
not been overlaid since the DCB was opened.
For return code 04, make sure that the SETPRT macro instruction
correctly specifies the address of an open DCB within your region.

Source
DFSMSdfp