RESUME Capability

If CVAF filter service terminates because you failed to provide sufficient buffers, the information necessary for a RESUME function is saved in the filter save area. (Specifying FLTAREA=KEEP on the initial CVAFFILT allocates the filter save area.)

To allow RESUME processing to execute correctly, you must maintain the relationship between the requested volume (identified by CVDEB, CVUCB, or a kept IOAREA), your FCL, and CVAF's FSA. If you observe this requirement, you can initiate and resume multiple CVAF filter service operations asynchronously on one or more DASD volumes. You can ensure this relationship by providing a unique CVPL and FCL for the duration of the READ/RESUME/RELEASE sequence associated with each logical request.

Issuing an ACCESS=RESUME without having previously specified FLTAREA=KEEP causes CVAF filter service to produce return code 4 in register 15 and 66 (decimal) in the CVSTAT field.

If you specify FLTAREA=KEEP, issue a subsequent CVAFFILT call with the ACCESS=RLSE keyword to release filter save area storage.

Figure 1. Control Blocks Required for CVAF Filter Services

Reg 1 ───→ CVPL──────┐
           ³  CVFCL ─┼──────────────────────────→ FCL───────┐
           ³         ³                            ³ FLCH    ³
           ³  CVBUFL─┼──→ BFL───────┐             ³         ³
           ³         ³    ³ BFLH    ³             ³ FCLDSN──┴┐
           ³         ³    ³         ³             ³ ³        ³
           └─────────┘    ³ BFLE────┴┐            ³ ³FCLDSNA─┼─→ DSN
                          ³ ³        ³            ³ └───────┬┘
                          ³ ³BFLEBUF─┼─→ DSCB     ³ FCLDSN──┴┐
                          ³ └───────┬┘    Buffer  ³ ³        ³
                          ³ BFLE────┴┐            ³ ³FCLDSNA─┼─→ DSN
                          ³ ³        ³            ³ └───────┬┘
                          ³ ³BFLEBUF─┼─→ DSCB     ³         ³
                          ³ └───────┬┘    Buffer  ³   ...   ³
                          ³         ³             ³         ³
                          ³   ...   ³             ³ FCLDSN──┴┐
                          ³         ³             ³ ³        ³
                          ³ BFLE────┴┐            ³ ³FCLDSNA─┼─→ DSN
                          ³ ³        ³            ³ └───────┬┘
                          ³ ³BFLEBUF─┼─→ DSCB     └─────────┘
                          ³ └───────┬┘    Buffer
                          └─────────┘