migration independent of the DFSMShsm system setting for SETSYS INTERVALMIGRATION command. Interval migration is performed on volumes that are at or above the midpoint between the high and low threshold. Interval migration is performed hourly. If a low threshold value of 0 is specified, DFSMShsm migrates all eligible data sets in the selected storage group. DFSMShsm on-demand migration is not performed. This value is most useful for storage groups used with tape mount management. P (primary) - This specifies that data sets are eligible for primary space management. Interval migration and on-demand migration are not performed regardless of the DFSMShsm system setting for SETSYS INTERVALMIGRATION and SETSYS ONDEMANDMIGRATION commands. Note: If for some reason (such as a system outage) system-managed temporary data sets are not deleted at the end of a job, DFSMShsm attempts to delete them during primary space management. For DFSMShsm to delete these data sets, you must specify Auto Migrate as Y, I, or P. Migration and allocation thresholds You can specify an upper and lower space limit for the DASD volumes in a pool storage group. SMS tries to stay within these thresholds by looking at the primary space allocation of each data set before assigning it to a given DASD volume. For example, the SMS volume selection function attempts to prevent allocation of a data set to a given DASD volume if that allocation causes the volume's high threshold to be exceeded. When a volume reaches or exceeds the high threshold, SMS issues an ENF72 signal, regardless of the Auto Migrate setting.