You can use IFG0EX0B to provide an installation-determined value for the number of buffers for QSAM DCBs, if a value has not yet been supplied. See Example of the IFG0EX0B Exit Routine.

• For QSAM DCBs, do not override a nonzero value in DCBBUFNO without knowing what dependency the user program might have on that value. If the DCBBUFCA field in the DCB contains a buffer pool control block address, it indicates that buffers have been acquired before open. Thus, you cannot override DCBBUFNO. After return from IFG0EX0B, if DCBBUFCA is zero, open turns on the low order bit (the absence of a buffer pool control block is indicated by the low order bit of DCBBUFCA being one). Unless the user specified RMODE31=BUFF in the DCBE, the user program is responsible for freeing buffer space after closing the DCB.
• For BSAM DCBs with DCBBUFCA set to one, do not override a zero value in DCBBUFNO without knowing what dependency the user program might have on that value. If the user program does not want open to acquire buffer storage space, it indicates this by setting DCBBUFNO to zero and DCBBUFCA to one. If the user program wants open to acquire buffer storage space, it can override DCBBUFNO with a nonzero value.