If the application requires that the CSM storage be pagefixed, the application must check the BLXEN_TYPE flag in the buffer list entry, ISTBLXEN. If the buffer is pageable, the application can use the IVTCSM REQUEST=FIX_BUFFER macroinstruction to ensure that the storage is pagefixed.
If the CSM storage received is from a data space, the application can gain addressability to the storage by using the ALET that is returned in the buffer list. The application can use the IVTCSM REQUEST=COPY_DATA macroinstruction if it needs to copy the data.
If the application wishes to perform I/O directly from the data space storage, it must build the I/O structures in accordance with the ESAME mode of the machine. When the machine is in ESAME mode, 64-bit I/O structures must be used. When the machine is not in ESAME mode, 31-bit I/O structures must be used.
In this case, CSM storage return responsibilities are transferred to a different process. The data must not be altered because the received data area is considered a read-only copy. The original requester of the CSM storage may have a CSM free routine outstanding and is entitled to the return of the storage with the data unaltered.