SELECT * FROM OAMADMIN.CBR_MGT_CLASS_TBL M, HLQ.OSM_OBJ_DIR D
WHERE   ODNAME = 'object_name'
AND     D.ODMCNUM = M.ODMCNUM;

List the ISMF definition of the management class. Be sure to specify ‘ACTIVE’ as the SCDS name. Examine the expiration attributes. If both EXPIRE AFTER DAYS NON-USAGE and EXPIRE AFTER DATE/DAYS are NOLIMIT, the object never expires. The value of EXPIRE AFTER DAYS NON-USAGE is added to the last referenced date (ODLREFDT) in the object directory table to calculate the expiration date. If the last referenced date is not set, the creation date is used. If the value of EXPIRE AFTER DATE/DAYS is an explicit date, that date is used as the expiration date. If the value is a number of days, the expiration date is calculated based on the number of days added to the creation date (ODCREATS) in the object directory table.

For additional information on expiration attribute processing, see z/OS DFSMSdfp Storage Administration.