Logical partitions (LPARs) are, in practice, equivalent to separate mainframes.
Each LPAR runs its own operating system. This can be any mainframe operating system; there is no need to run z/OS®, for example, in each LPAR. The installation planners may elect to share I/O devices across several LPARs, but this is a local decision.
The system administrator can assign one or more system processors for the exclusive use of an LPAR. Alternately, the administrator can allow all processors to be used on some or all LPARs. Here, the system control functions (often known as microcode or firmware) provide a dispatcher to share the processors among the selected LPARs. The administrator can specify a maximum number of concurrent processors executing in each LPAR. The administrator can also provide weightings for different LPARs; for example, specifying that LPAR1 should receive twice as much processor time as LPAR2.
- LPAR will be created by DEFINE LPAR lparname CSS01 MIF_id 3
In mainframe computing a PR/SM (Processor Resource/System Manager) is a type-1 Hypervisor (a virtual machine) that allows multiple logical partitions to share physical resources such as CPUs, I/O channels and direct access storage devices (DASD). It is integrated with all IBM System z machines.