From the viewpoint of the user, an SM pubset appears as a file container which provides specific file management services. These are called file services. They can be subdivided into
storage services (e.g. performance, availability offered)
HSMS management services (e.g. controlling file migration to background levels, controlling the creation of file backups) .
The user requests the file services he requires by means of file attributes for which appropriate values must be assigned to the files.
Storage services
Systems support can set up storage classes which represent a specific combination of values for the file attributes relevant to storage location (see the CREATE-STORAGE-CLASS and MODIFY-STORAGE-CLASS (EDIT-STORAGE-CLASS) commands).
The user selects the storage class for a file which fulfills the requirements for a file most closely (see the STORAGE-CLASS operand of the CREATE-FILE or MODIFY-FILE-ATTRIBUTES command). He/She does not have to enter the values individually.
The storage service requested by the user for a file is taken into account when:
a file is created
a file is moved from a background level to the processing level
for an existing file the user modifies the file attributes relevant to storage location in such a way that it is incompatible with the previous storage location
The system automatically determines the most suitable volume set
Systems support can define a default storage class for every user. This can make some direct attributes ineffective when there are no rights to physically edit attributes.
Volume set lists
The system behavior can be influenced by volume set lists which systems support configures and links to storage classes (see the VOLUME-SET-LIST operand of the CREATE-VOLUME-SET-LIST and CREATE-STORAGE-CLASS commands).
If a user assigns a file a storage class to which a volume set list is assigned, the system stores the file with priority on a volume set belonging to this volume set list. If the file already occupies storage space on another volume set, it is, if possible, relocated from this volume set to one of the preferred volume sets. Files which are assigned no storage class or a storage class without a volume set list are stored with priority on volume sets which do not belong to any of the volume set lists configured by systems support.
HSMS management services
Management services are requested using HSMS management classes. They must be set up by systems support (HSMS statement CREATE-MANAGEMENT-CLASS). The HSMS management classes represent specific methods of data backup (e.g. backup frequency, lifetime of backup versions, etc.) and rules which control the migration to background levels (e.g. suitability for migration, dependent on the time since the last access).
When the user assigns a file to an HSMS management class (MANAGEMENT-CLASS operand of the CREATE-FILE or MODIFY-FILE-ATTRIBUTES command), it is submitted to the backup or migration methods which are represented by this HSMS management class. The user can exclude particular files from being migrated to background levels either generally or under specific conditions (MIGRATE operand of the CREATE-FILE and MODIFY-FILE-ATTRIBUTES commands). If necessary, the user must have allowance for physical allocation.