Issuing the DEFINE ARPOOL command

The DEFINE ARPOOL command allows you to determine the target DASD level 0 and ML1 volumes to be used for aggregate recovery. These are the volumes used as target volumes for migrated and DASD data sets that have not had their allocation directed to other volumes by SMS. Data sets can have their allocations directed by SMS only when it is installed and active at the recovery site.

To ensure that the settings are defined to DFSMShsm at startup initialization, you should include the DEFINE command in the DFSMShsm parmlib member (ARCCMDxx). If you are an authorized DFSMShsm user, you can issue the DEFINE command before an aggregate recovery to modify existing pool configurations or add new pools.

To specify a pool of volumes to be used as target volumes for data sets recovered by aggregate recovery, use the ARPOOL(agname) parameter. The aggregate group name (agname) identifies a pool and relates that set of volumes to an aggregate group that was previously backed up with the ABACKUP command. These volumes are used as output volumes when the application is recovered. If an aggregate group name of * is specified, the volumes are assigned to a general pool of aggregate recovery volumes. A general pool is a group of volumes defined for recovering those aggregate groups for which no specific pool has been defined. If no aggregate group name is specified, the DEFINE command fails.
Note: Even though ABARS supports a general pool of volumes for all aggregates, you should define individual aggregate recovery pools for each aggregate. Define these pools so that the order of the volumes is varied, especially for those volumes defined with the ML1VOLS parameter. For example: 
DEFINE ARPOOL(AGG1 ML1VOLS(VOL1,VOL2,VOL3) -
   L0VOLS(VOLA,VOLB,VOLC))

DEFINE ARPOOL(AGG2 ML1VOLS(VOL2,VOL3,VOL1) -
   L0VOLS(VOLB,VOLC,VOLA))

DEFINE ARPOOL(AGG3 ML1VOLS(VOL3,VOL1,VOL2) -
   L0VOLS(VOLC,VOLA,VOLB))

The volumes defined with the ML1VOLS parameter are serially loaded in the order in which they are defined. If several aggregate recoveries are processing with ARPOOLs that have the same volume serial numbers in the same order, then volume and channel contention are increased. Varying volume order prevents different aggregate recoveries from attempting to use the same volumes. It is apparent that this is especially critical if multiple ARECOVER commands are processing simultaneously.

ALL specifies that all currently mounted ADDVOLed level 0 and ML1 volumes are to be defined to the volume pools for aggregate recovery. It is equivalent to specifying the L0VOLS(*) and ML1VOLS(*) parameters.

ML1VOLS(volser1,...volsern | *) specifies a list of non-SMS-managed volumes to be used as target volumes to recover migrated data sets. If * is specified, all currently mounted ADDVOLed ML1 volumes are used as the pool of ML1 volumes for aggregate recovery.

L0VOLS(volser1,...volsern | *) specifies a list of non-SMS-managed volumes to be used as target volumes to recover nonmigrated, non-SMS-managed data sets. If * is specified, all currently mounted ADDVOLed primary volumes are used as the pool of level 0 volumes for aggregate recovery.
Note: If insufficient space is defined, the data set recovery fails. If the level 0 or ML1 volumes specified in the pool are not online and mounted, aggregate recovery fails.

If the DEFINE ARPOOL command is issued without the ALL, ML1VOLS, and L0VOLS parameters, the aggregate recovery pool specified by agname is deleted. If an aggregate group name of * is specified, the general pool of aggregate recovery volumes is deleted.

If a DEFINE ARPOOL command was not previously issued before an ARECOVER command, DFSMShsm uses all currently mounted ADDVOLed primary (59 maximum) and ML1 volumes as the ARPOOL.

The aggregate recovery pools that have been defined can be displayed by using the QUERY ARPOOL command.If L0VOLS have been specified, these volume serial numbers are passed to ACS by DFSMSdss. ACS routines may then use these volume serial numbers to determine the classes and placement of the data sets.

If ACS does not assign storage classes to the data sets, then DFSMSdss attempts to direct allocation to the volume serial number where the data set resided when backed up. If that particular volume serial number does not exist at the recovery site, recovery of the data set in question fails. In a non-SMS environment, all level 0 data sets are directed to L0VOLS volumes.

The ARPOOL volumes need not be added to DFSMShsm using the ADDVOL command before issuing the DEFINE ARPOOL command; however, the following restrictions apply to the relationship between DFSMShsm-owned and -managed volumes and volumes assigned to the aggregate recovery pool:
  • A volume previously added to DFSMShsm as anything other than a PRIMARY volume cannot be defined with the L0VOLS parameter of the DEFINE ARPOOL command.
  • A volume previously added to DFSMShsm as anything other than an ML1 volume cannot be defined with the ML1VOLS parameter of the DEFINE ARPOOL command.
  • A volume previously defined to aggregate recovery with the ML1VOLS parameter of the DEFINE ARPOOL command can subsequently be added to DFSMShsm only as an ML1 volume.
  • A volume previously defined to aggregate recovery with the L0VOLS parameter of the DEFINE ARPOOL command can subsequently be added to DFSMShsm only as a PRIMARY volume.
  • A volume cannot be SMS managed.
  • A volume defined as L0VOLS cannot also be defined as ML1VOLS. Conversely, a volume defined as ML1VOLS cannot also be defined as L0VOLS. This is true whether it conflicts with a previously defined pool or whether a conflict exists within the pool being defined.

You should use the ADDVOL command to add all aggregate recovery volumes to DFSMShsm as soon as possible after an ARECOVER command has successfully completed processing. If you do not do this, failures can occur when an attempt is made to refer to those data sets.

Related reading

Parent topic: Preparing for aggregate recovery