The following document from the IBM Knowledge Center describes the implications of setting RSU=0;
Basically, setting RSU=0 (default) means one of two things;
- You are not using PR/SM
- You are not allowing PR/SM to perform dynamic storage reallocation for your LPARs.
So, by setting RSU=0, means that you are not making any of your CPC storage available for dynamic reconfiguration. If you put a non-zero value (and unit, like MB, GB) after RSU=, then that’s the amount of central storage that you are reserving for dynamic reconfiguration use.
To see how much storage is allocated to each LPAR on your CPC, you can look at these two data elements in the HARLPC file:
LPCCSF – Central Storage Megabytes Assigned
LPCESF – Expanded Storage Megabytes Assigned
To see the breakout of various storage areas for paging, you can examine the data elements in the SCPPAG file for each z/OS LPAR.