JCL DD statement: ddnames that are reserved for specific uses

JCL programmers can use almost any name as a label for a DD statements, but IBM® reserves this list of ddnames for special-function DD statements.

Use the following special ddnames only when you want to use the facilities these names represent to the system:

JOBLIB: A JOBLIB DD statement, placed just after a JOB statement, specifies a library that should be searched first for the programs executed by this job.
STEPLIB: A STEPLIB DD statement, placed just after an EXEC statement, specifies a library that should be searched first for the program executed by the EXEC statement. A STEPLIB overrides a JOBLIB if both are used.
SYSCHK: The SYSCHK DD statement defines a checkpoint data set that the system is to write during execution of a processing program.
SYSCKEOV: The SYSCKEOV DD statement defines a checkpoint data set for checkpoint records from the checkpoint at end-of-volume (EOV) facility. The checkpoint at EOV facility is invoked by a DD CHKPT parameter.
SYSIN: By convention, people often use a SYSIN DD statement to begin an in-stream data set.
SYSABEND, SYSUDUMP, SYSMDUMP and CEEDUMP: The SYSABEND, SYSUDUMP, SYSMDUMP, and CEEDUMP DD statements are used for various types of memory dumps that are generated when a program abnormally ends.

Another set of reserved ddnames, JOBCAT and STEPCAT, are used to specify private catalogs, but these are rarely used (the most recent z/OS® releases no longer support private catalogs). Nevertheless, these DD names should be treated as reserved names.

The following ddnames have special meaning to JES2; do not use them on a DD statement in a JES2 system.

JESJCL
JESJCLIN
JESMSGLG
JESYSMSG

The following ddnames have special meaning to JES3; do not use them on a DD statement in a JES3 system.

J3JBINFO
J3SCINFO
J3STINFO
JCBIN
JCBLOCK
JCBTAB
JESInnnn
JESJCL
JESJCLIN
JESMSGLG
JESYSMSG
JOURNAL
JS3CATLG
JST
STCINRDR
TSOINRDR