Active control data set (ACDS)

When you activate an SCDS, its contents are copied to an ACDS. The current ACDS contains a copy of the most recently activated configuration. All systems in an SMS complex use this configuration to manage storage. You can define any number of SCDSs, but only one can be put in the ACDS. z/OS MVS Initialization and Tuning Guide explains how to specify the ACDS. You can define more than one IGDSMSxx member, each specifying a different ACDS, but you can use only one ACDS at a time.

Tip: You can save the current ACDS as an SCDS using the SETSMS SAVESCDS command. You can also create an ACDS from a SCDS with the SETSMS COPYSCDS command. For more information, see Parameters of the SETSMS operator command.

Restriction: You cannot define or alter an ACDS. This also means that you cannot use an ACDS as an SCDS if the SCDS is lost.

You can modify the SCDS from which your current storage management policy was activated without disrupting operations, because SMS manages storage with a copy of the SMS configuration (an ACDS) rather than with the original (an SCDS). While SMS manages storage using an ACDS, you can:

Create a backup copy of the SCDS
Build a new SCDS
Update the SCDS from which the ACDS was activated
Modify any SCDS

Figure 1 shows the relationship among SCDSs and ACDSs in an installation.

Figure 1. Relationship among SCDSs and ACDSs in an Installation

An installation may have several SCDSs, each containing one storage management policy, and a few ACDSs, which contain the currently active SMS configuration (storage management policy). Only one ACDS can be active at a time.