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DAT (Dynamic Address Translation)

Note that the user’s programs run in a logical address space meaning that the operating system needs a mechanism to translate references to logical addresses to real addresses.

  • This is a z/OS hardware capability that allows the user’s virtual addresses to be translated into real addresses when interpreted by the processor.

Data Set

In general, a data set is functionaly the same as a Unix file even though data sets are structurally different from Unix files.

  • Functionally speaking, a data set is just a file.

DASD (Direct Access Storage Device)

This is like the z/OS version of the SSDs and hard drives you use on your PC.

  • A disk/storage device.


Note that DB2 is optimized to leverage z/OS capabilities.

  • This is a relational database like MySLQ or PostgreSQL.

DCB attribute (Data Control Block Attribute)

  • This is the metadata or information that describes a data set (type, record format, logical record length, etc).

DD (Data Set Definition)

  • This is how you define the input data sets that are to be use in a JCL job step.

DFSMS (Data Facility Storage Management)

  • z/OS component for managing storage.


  • Part of DFSMS that provides functions for storage, data, device, and program management.


  • Part of DFSMS that provides utilities for copying and moving data.

DFSMShsm (DFSMS Hierarchical Storage Manager)

  • Data storage technique that moves data between low and high cost storage devices. DFSMShsm also provides backup and disaster recovery capabilities.


  • Part of DFSMS that provides functions for managing tape.

DLIB (Distribution Library)

  • Contains an entire copy of the z/OS product. This is used by SMPE as a local repository where new APARs and PTFs can be added, and the updates can be installed from this repository when the organization is ready. DLIBs may also be used for backup.

DSLIST (Data Set List)

This is analogous to the ls command on Linux.

  • This is the panel in ISPF used to list data sets.

DSN (Data Set Name)

  • The name of a data set.

DYNALLOC (Dynamic Allocation)

  • TODO