Working set management

SRM automatically determines the best mix of work in the multiprogramming set (MPS) and the most productive amount of central storage to allocate to each address space within MPL constraints.

To achieve this, SRM monitors the system paging, page movement, and swapping rates and productive CPU service for all address spaces to detect when the system might run more efficiently with selected address space working sets managed individually. If the system is spending a significant amount of resources for paging, SRM will start monitoring the central storage of selected address spaces.

After SRM decides that an address space should be monitored, SRM collects additional address space data. Based on this data, SRM might discontinue implicit block paging.

For monitored address spaces, SRM calculates a working set manager recommendation value that can override the swap recommendation value. See Swap recommendation value for information about the swap recommendation value. The working set manager recommendation value measures the value of adding the address space to the current mix of work in the system. Even when the swap recommendation value indicates that a specific address space should be swapped in next, the working set manager recommendation value might indicate that the address space should be bypassed. To ensure that no address space is repeatedly bypassed, the system swaps in a TSO/E user 30 seconds after being bypassed. For all other types of address spaces, the system will swap in the address space 10 minutes after being bypassed.

If a monitored address space is paging heavily, SRM might manage its central storage usage. When an address space is managed, SRM imposes a central storage target (implicit dynamic central storage isolation maximum working set) on an address space.