Allocating SMS Control Data Sets

SMS stores its class and group definitions, translated ACS routines, and system information in the following three control data sets:

The SCDS contains a set of SMS classes and groups and translated ACS routines that implement a specific set of storage management policies.
This is the source control data set, the SMS configuration that you develop and test. You can have several SCDSs. One should correspond to your current policies. Retain at least one prior configuration should you need to regress to it because of error. The SCDS is never used to manage allocations.
The ACDS is the system's active copy of the current SCDS.
Recommendation: Ensure that you have extra ACDSs in case a hardware failure causes the loss of your primary ACDS. It must reside on a shared device, accessible to all systems, to ensure that they share a common view of the active configuration. Do not have the ACDS reside on the same device as the COMMDS or SCDS. Both the ACDS and COMMDS are needed for SMS operation across the complex. Separation protects against hardware failure. You should also create a backup ACDS in case of hardware failure or accidental data loss or corruption.
The COMMDS enables communication of configuration changes between SMS systems in a multisystem environment.
It contains the name of the ACDS containing the active storage management policy, and storage group volume statistics. The COMMDS must reside on a shared device accessible to all systems. However, do not allocate it on the same device as the ACDS. Create a spare COMMDS in case of a hardware failure or accidental data loss or corruption. SMS activation fails if the COMMDS is unavailable.