Auxiliary storage overview

Auxiliary storage DASD hard disk drives are required on z/OS® systems for storing all system data sets. For additional paging flexibility and efficiency, you can add optional storage-class memory (SCM) on Flash Express® solid-state drives as a second type of auxiliary storage.

You must have enough auxiliary storage available to store the programs and data that comprise your z/OS system. This auxiliary storage that supports basic system requirements has three logical areas (see Figure 1):

System data set storage area.
Paging data sets for backup of all pageable address spaces.
TSO data sets.

If your auxiliary storage includes SCM on Flash drives, you must be aware of the data storage requirements and limitations for each storage medium, which are described in the following sections. Refer to Auxiliary storage management initialization, and to the PAGE, PAGESCM, NONVIO and PAGTOTL parameters (IEASYSxx PARMLIB member) in z/OS MVS Initialization and Tuning Reference.