z/OS MVS JCL Reference
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Storing a dump

z/OS MVS JCL Reference

If you wish to store a dump instead of having it printed, code the following parameters on the dump DD statement:
  • The DSNAME parameter.
  • The UNIT parameter.
  • The VOLUME parameter. This parameter is optional and not recommended. The system will select a volume.
  • The DISP parameter. The data set’s status is NEW. Because you want to store the data set, make the data set’s abnormal termination disposition KEEP or CATLG.
  • The SPACE parameter, if the dump is written on direct access.

Tip: SYSABEND, SYSUDUMP, and SYSMDUMP can use extended format sequential data sets to exploit striping, compression, or both. Striping speeds the writing process and compression reduces the space consumed and speeds the I/O bound dump process. Extended format sequential data set hold more than 64K tracks per volume making it an attractive destination for dumps. DSNAME=LARGE also allows data sets to use more than 64K tracks per volume.

Note: Do not use VSAM for dump data sets.

SYSMDUMP Requirements: The SYSMDUMP DD statement must specify a magnetic tape unit or a direct access device. Do not direct SYSMDUMP to SYSOUT.

With the exception of the following facility, the system processes dump data sets according to the disposition to which they are allocated. To keep only the first SYSMDUMP dump written to a dump data set, specify the following on the SYSMDUMP DD statement:
  • DSNAME=SYS1.SYSMDPxx, where xx is 00 through FF and indicates the specific dump data set to be used. SYSMDPxx is a preallocated data set that must have end-of-file (EOF) mark as its first record.
  • FREE=CLOSE for multiple job steps
Note: This restriction is not enforced. If SYSOUT is used, the resulting dump will be unusable for diagnosis.

See z/OS MVS Diagnosis: Tools and Service Aids for a description of the SYS1.SYSMDPxx naming convention and an explanation of how the system manages the dump data sets.

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