CSM buffer pools are expanded as needed to maintain the specified number of free buffers in the pool. The number of free buffers maintained is determined by the highest MINFREE (minimum free buffer) specifications by all users of a pool.

CSM buffer pools are expanded by the maximum of the EXPBUF (expand buffers) specifications by all users of a pool. The storage pool is expanded if the number of free buffers falls below MINFREE.

The pool is managed in extents. Expansion consists of creating a new extent with the number of buffers as determined by the EXPBUF parameters. The expansion of the pool is scheduled as a side process in order to avoid excessive pathlength on a IVTCSM REQUEST=GET_BUFFER macroinstruction due to inline pool expansion. In the event that pool expansion must complete to satisfy a request for buffers, the application can optionally wait for pool expansion to complete by specifying WAIT=EXPAND or WAIT=YES on the IVTCSM REQUEST=GET_BUFFER macroinstruction.