Specifying the maximum interval migration or on-demand migration tasks

DFSMShsm allows up to 15 interval migration or on-demand migration tasks to run concurrently in each DFSMShsm host during automatic interval or on-demand space management. Use the MAXINTERVALTASKS parameter of the SETSYS command to control the maximum number of interval migration or on-demand migration tasks that you want to run concurrently. If you do not specify MAXINTERVALTASKS on any SETSYS command, it defaults to the value of MAXMIGRATIONTASKS.

Note: MAXEVENTDRIVENMIGTASKS or the MAXEDMT alias can be used instead of the MAXINTERVALTASKS parameter.

If migration is to tape, a tape unit is required for each concurrent interval migration or on-demand migration task that migrates a data set directly to tape. If using the duplex tape option, two tape units per task are required. Tape units are allocated when a task encounters the first data set being migrated to tape, and the task does not release the tape units until it has completed processing all volumes. If migration is to SDSP data sets, an SDSP data set is needed for each concurrent interval migration or on-demand migration task being performed. An SDSP data set is allocated when a task encounters the first data set that is being migrated to an SDSP. The task does not release the SDSP until the entire volume has been processed unless it remains unused for 30 seconds or the functions RECALL or ABACKUP need the SDSP data set.

Note: The actual number of migration tasks can be equal to the number of tasks specified on the MAXMIGRATIONTASKS or the MAXINTERVALTASKS and up to twice the specified number of tasks because of DFSMShsm's preprocessing enhancement. This is reflected in a number of ARC0161I messages issued in response to the QUERY ACTIVE or QUERY ACTIVE(TCB) commands. MIGRATING, MIGRATION PREPROCESSING, FREEVOL PROCESSING, and DBA/DBU PROCESSING differentiate the type of space management DFSMShsm is performing and these are displayed in the ARC0161I message.

Migration tasks perform all space management tasks, including class transitions. Class transitions have a higher priority than migrations and will be processed first during the data movement phase. If a data set is eligible for both a class transition and migration, then it will be migrated.