Central storage

Throughout this document there are statements that state "Sharing of allocated central storage among multiple logical partitions is not allowed", and " ... it becomes available to the logical partition if no other logical partition is using the same storage. This is because PR/SM has a mechanism that detects conditions where sharing was defined (where address ranges overlap), and rejects such requests. PR/SM licensed internal code (LIC) and hardware rigidly enforce the no-sharing rule at logical partition definition, during logical partition activation, during logical partition reconfiguration, and during logical partition execution. PR/SM monitors each instruction's storage accesses for validity; accesses outside the logical partition's defined storage are not permitted to proceed.

Only storage increments within the logical partition's storage allocation as defined in the activation profile can be placed offline. For z/OS System Control Program (SCP) partitions, storage is varied off and on line by using the z/OS® CONFIG (CF) operator command. See z/OS MVS System Commands for further detail. While processing this command, MVS must interact with PR/SM, through a service call instruction, to request that the storage be varied. Because storage cannot be varied without PR/SM involvement, no way exists to circumvent the validity checking PR/SM does to confine a partition occupant within the storage limits defined for the logical partition.