SMS Control Data sets - Restrictions/Recommendations

Resolving The Problem

SMS control data sets (SCDS, ACDS and COMMDS) are VSAM linear which can be either SMS-managed or non-SMS-managed.

There are some restrictions/recommendations around these SMS CDS's such as:

• Initially, ensure that your control data sets have a volume count of one (volume count = 1 with no DVC in the data class).

The SMS-managed control data sets (SCDS, ACDS, and COMMDS) can be defined as multivolume. In this case, please, read the information/restrictions described in the following link:

https://www.ibm.com/docs/en/zos/3.1.0?topic=sets-selecting-volumes-control-data

• Do not allocate control data sets as extended format VSAM linear data sets.
• Do not allocate control data sets as encrypted VSAM linear data sets.
• They can be defined in a user catalog but do not catalog the SMS control data sets (SCDS, ACDS, COMMDS) in a user catalog that is RLS-managed.
• Define SCDS, ACDS and COMMDS with the REUSE option
• Define ACDS and COMMDS on separate volumes to ease recovery in case of failure
• ACDS and COMMDS must reside on a shared volume accessible from all systems in the SMS complex and that is not reserved by other systems for a long period of time because the control data set (ACDS or COMMDS) must be available to access for SMS processing to continue.
• Use SHAREOPTIONS(3,3) when allocating an ACDS or COMMDS
• Use SHAREOPTIONS(2,3) when allocating SCDS
• To calculate the size of both SMS CDS's please follow the rules from links below "Calculating the size of storage and active control data sets" and "Calculating the size of a COMMDS"

Links suggested:

• Defining the Storage Management Subsystem Configuration: https://www.ibm.com/docs/en/zos/3.1.0?topic=sms-defining-storage-management-subsystem-configuration
• Allocating SMS Control Data Sets: https://www.ibm.com/docs/en/zos/3.1.0?topic=subsystem-allocating-sms-control-data-sets
• Allocating control data sets : https://www.ibm.com/docs/en/zos/3.1.0?topic=subsystem-allocating-control-data-sets
• Example: Allocating Control Data Sets : https://www.ibm.com/docs/en/zos/3.1.0?topic=sets-example-allocating-control-data
• Recommendations : https://www.ibm.com/docs/en/zos/3.1.0?topic=sets-recommendations
• Recovering control data sets: https://www.ibm.com/docs/en/zos/3.1.0?topic=information-recovering-control-data-sets
• Selecting volumes for control data sets: https://www.ibm.com/docs/en/zos/3.1.0?topic=sets-selecting-volumes-control-data
• Calculating the size of storage and active control data sets : https://www.ibm.com/docs/en/zos/3.1.0?topic=sets-calculating-size-storage-active-control-data
• Calculating the size of a COMMDS : https://www.ibm.com/docs/en/zos/3.1.0?topic=sets-calculating-size-commds