Any buffer pool assigned to a DCB either automatically by the OPEN macro (except when dynamic buffer control is used or the system is honoring RMODE31=BUFF on the DCBE macro), or explicitly by the GETPOOL macro should be released before your program is completed. The FREEPOOL macro should be issued to release the virtual storage area when the buffers are no longer needed. When you are using the queued access technique, you must close the data set first. If you are not using the queued access method, it is still advisable to close the data set first.

If the OPEN macro was issued while running in problem state, protect key of zero, a buffer pool that was obtained by OPEN should be released by issuing the FREEMAIN macro instead of the FREEPOOL macro. This is necessary because the buffer pool acquired under these conditions will be in storage assigned to subpool 252 (in user key storage).