Transition data sets that are candidates for a class transition

Data sets that are eligible for a class transition are processed first. If a data set is eligible for both a class transition and migration, then the data set will be migrated.

When a data set meets the management class criteria for a class transition, then DFSMShsm invokes the ACS routines with the ACS environment SPMGCLTR to determine if there is a newly assigned management class, storage class or storage group. If that data set is assigned a new management class and the storage class and storage group remain unchanged, then DFSMShsm will ALTER that data set to reassign the data set to the newly assigned management class. No data movement will occur. The newly assigned management class will be used to determine how the data set is managed during future space management processing.

If a data set is assigned a new storage class or storage group, then the data set will be moved. DFSMShsm will invoke DFSMSdss to move the data set with the logical data set copy and delete operation. This process will invoke SMS to use the newly assigned storage class and/or storage group for the allocation.

Data sets are transitioned until the occupied space is equal to or less than the low threshold specified by the storage group or until no more class transition candidates exist on the volume. If the low threshold has been met, DFSMShsm ends automatic primary space management processing for that volume. If the low threshold has not been met, then primary space management processing continues for migration and extent reduction candidates.

DFSMShsm does not keep any records for transitioned data sets within its control data sets. Function Statistics Records (FSR) are used to track transition processing. Storage administrators may use the various reporting techniques available for FSR records to analyze DFSMShsm's class transition processing. A sample report is provided for the DFSMS Report Generator. (See Running new reports with report generator.) The DFSMShsm REPORT function also provides basic reporting information.

By default, failing messages are not issued for data sets that fail a transition because exclusive serialization could not be obtained. It is recommended that these data sets be analyzed by post processing the FSR records with failing return code RC68 and reason code REAS410. If desired, the patch offset which enables these messages is:

PATCH .MGCB.+EF BITS(...1....)