DFSMShsm uses cell pools (the MVS™ CPOOL function) to allocate virtual storage for frequently used modules and control blocks. Cell pool storage used for control blocks is extendable, while cell pool storage used by modules is not. Using cell pools reduces DFSMShsm CPU usage and improves DFSMShsm performance. The DFSMShsm startup procedure specifies the size (in number of cells) of five cell pools used by DFSMShsm.

DFSMShsm is configured with a default size for each cell pool. You can change these sizes by changing the CELLS keyword in the startup procedure for the DFSMShsm primary address space. Typically the default values are acceptable. However, if you run many concurrent DFSMShsm tasks, you may receive an ARC0019I message, which identifies a cell pool that has run out of cells. If you receive this message, you should increase the size of the indicated cell pool by at least the number of cells specified in the message.