anyname DD Statement

A DD statement must be included for each permanently mounted or mountable volume referred to in the job step. These DD statements are used as device allocation statements, rather than as true data definition statements.

This DD statement can be entered:

  //anyname DD UNIT=xxxx,VOLUME=SER=xxxxxx,
DISP=OLD

The UNIT and VOLUME parameters define the device type and volume serial number. The DISP=OLD specification prevents the inadvertent creation of a data set.

Because IEHPROGM modifies the internal control blocks created by device allocation DD statements, the DSNAME parameter, if supplied, will be ignored by IEHPROGM. (All data sets are defined explicitly or implicitly by utility control statements.)

Note: Unpredictable results may occur in multitasking environments where dynamic allocation/deallocation of devices, by other tasks, causes changes in the TIOT during IEHPROGM execution.

To specify deferred mounting with mountable volumes, code:

  //anyname DD  VOLUME=(PRIVATE,SER=xxxxxx),
  //            UNIT=(xxxx,,DEFER),DISP=OLD

Unit affinity cannot be used on DD statements defining mountable devices.