what is an lpar in mainframe
On IBM mainframes, LPARs are managed by the PR/SM facility. IBM mainframes operate exclusively in LPAR mode, even when there is only one partition on a machine. Multiple LPARs running z/OS can form a Sysplex or Parallel Sysplex, whether on one machine or spread across multiple machines.BM introduced the Start Interpretive Execution (SIE) instruction (designed specifically for the execution of virtual machines) as part of 370-XA architecture on the 3081, as well as VM/XA versions of VM to exploit it.