LPAR

Logical PARtiton is a "slice" of a mainframe system created by the PRSM system, each instance of an operating system will receive one LPAR. A z16 mainframe can have up to 85 LPARs

Each one will be assigned a smaller subset of the systems resources, for example if you have 15 CPUs and 600 GB of ram you can assign 5 CPUs and 200GB of ram to each of the 3 LPARS (though you can divide them how you want).

If the CPU wanted by another LPAR is busy, the LPAR will have to wait until the CPU frees up, or the PRSM decides it's CPU time is up.