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System Managed Storage Concepts and Components 29
by issuing specific commands when manual operations are appropriate. Volumes
can be:
• Managed by SMS. In this case the Storage Group definitions controls HSM
initiated automatic functions, depending upon the appropriate Management
Class of the data set.
• Managed by HSM. These volumes are commonly known as primary or level 0.
Here each volume is defined to HSM individually by the ADDVOL parameter
and governed accordingly.
• Owned by HSM. These incorporate migration level 1 (ML1), migration level 2
(ML2), backup, dump and aggregate volumes, and are a combination of disk
and tape. Alternate tape copies can be made of ML2 and backup tapes for
off-site storage. Also, spill volumes can be generated from backups and ML2
volumes to improve tape usage efficiency.
Figure 10 shows the relationship between the main components of the HSM
environment.
Figure 10. DFSMShsm Components
4.3.3.1 Space Management
On a daily basis, HSM performs automatic space management,
depending upon whether the volume is part of an SMS Storage Group
or managed individually by HSM. Space management consists of the
following functions:
•Migration
This is the process of moving eligible, inactive, cataloged data sets to
either ML1 or ML2 volumes, from primary volumes (Level 0). This is
DFSMShsm Environment
SMS
Storage
Groups
ML1
HSM
Primary
Volumes
Recover
Dump
ABARS
Recycle
Incremental
Backup
Spill
Level 0
ML2
Recycle
Recall