Systems support must ensure that the volume set properties profiles are fulfilled by the physical volume set configuration.
Physical properties of the separate volumes
The physical properties of a volume set are determined by the properties of the volumes belonging to it and their I/O configuration (controllers, access paths, etc.). The volume configuration of the volume sets should be homogeneous so that meaningful properties profiles can be assigned to the volume sets, i.e. systems support should only group volumes together into a volume set whose properties harmonize with the intended properties profile. With specific properties, the volume set homogeneity is forced by the system (e.g. allocation unit size, format).
Maximum input/output length
The maximum input/output length is the maximum number of blocks which can be transferred for an I/O request. It is determined by the device type. The maximum input/output length is determined by the smallest value for all volumes in the volume set. If an additional volume is added to a volume set, the maximum input/output length of the volume set may be reduced. The maximum input/output length of a volume set is used by certain privileged applications (ARCHIVE, COPY) for optimizing I/O operations.
The maximum input/output length of a volume set can be displayed with the SHOW-PUBSET-CONFIGURATION command.
Volume sets as independent failure units
Volume sets of an SM pubset can (with the exception of the control volume set) be created as independent failure units.
For this purpose these volume sets must be mapped to physical configurations which are independent of each other with respect to failure. For example, the access paths (channels, controllers, etc.) to the volumes of volume sets which are to be independent with respect to failure, must be decoupled from each other. The cache configurations assigned to the volume sets must also be considered.
DRV functions can be used for providing volume sets which are particularly secure against failure. These functions provide a similar user interface for SM pubsets at the volume set level as for SF pubsets at pubset level. Shared pubsets cannot be operated with DRV.