Control Interval Splits

Some control interval splits involve data being moved to two new control intervals, and control area splits normally involve many control intervals' contents being moved. In these cases, VSAM exits to the JRNAD routine for each separate movement of data to a new control interval.

You might also want to use the JRNAD exit to maintain shared or exclusive control over certain data or index control intervals; and in some cases, in your exit routine you can reject the request for certain processing of the control intervals. For example, if you used this exit to maintain information about a data set in a shared environment, you might reject a request for a control interval or control area split because the split might adversely affect other users of the data set.

Figure 1 is a skeleton program USERPROG with a user exit routine USEREXIT. It demonstrates the use of the JRNAD exit routine to cancel a request for a control interval or control area split.

Figure 1. Example of a JRNAD exit Part 1 of 2

USERPROG  CSECT
          SAVE(R14,R12)       Standard entry code
          .
          .
          .
          BLDVRP BUFFERS=(512(3)),  Build resource pool               X
                KEYLEN=4,                                             X
                STRNO=4,                                              X
                TYPE=LSR,                                             X
                SHRPOOL=1,                                            X
                RMODE31=ALL
          OPEN (DIRACB)       Logically connect KSDS1
          .
          .
          .
          PUT RPL=DIRRPL      This PUT causes the exit routine USEREXIT
                              to be taken with an exit code X'50' if
                              there is a CI or CA split
          LTR R15,R15         Check return code from PUT
          BZ NOCANCEL         Retcode = 0 if USEREXIT did not cancel
                                          CI/CA split
                                      = 8 if cancel was issued, if
                                          we know a CI or CA split
                                          occurred
          .
          .                   Process the cancel situation
          .
NOCANCEL  .                   Process the noncancel situation
          .
          .
          CLOSE (DIRACB)      Disconnect KSDS1
          DLVRP TYPE=LSR,SHRPOOL=1  Delete the resource pool
          .
          .
          .
          RETURN              Return to caller.
          .
          .
          .
DIRACB    ACB AM=VSAM,                                                X
          DDNAME=KSDS1,                                               X
          BUFND=3,                                                    X
          BUFNI=2,                                                    X
          MACRF=(KEY,DDN,SEQ,DIR,OUT,LSR),                            X
          SHRPOOL=1,                                                  X
          EXLST=EXITLST

Figure 2. Example of a JRNAD exit Part 2 of 2

*
DIRRPL    RPL AM=VSAM,                                                X
          ACB=DIRACB,                                                 X
          AREA=DATAREC,                                               X
          AREALEN=128,                                                X
          ARG=KEYNO,                                                  X
          KEYLEN=4,                                                   X
          OPTCD=(KEY,DIR,FWD,SYN,NUP,WAITX),                          X
          RECLEN=128
*
DATAREC   DC  CL128'DATA RECORD TO BE PUT TO KSDS1'
KEYNO     DC  F'0'            Search key argument for RPL
EXITLST   EXLST AM=VSAM,JRNAD=(JRNADDR,A,L)
JRNADDR   DC  CL8'USEREXIT'   Name of user exit routine
          END                 End of USERPROG
 
 
USEREXIT  CSECT               On entry to this exit routine, R1 points
                              to the JRNAD parameter list and R14 points
                              back to VSAM.
          .
          .                   Nonstandard entry code -- need not save
          .                   the registers at caller's save area and,
          .                   since user exit routines are reentrant for
          .                   most applications, save R1 and R14 at some
          .                   registers only if R1 and R14 are to be
          .                   destroyed
          .
          CLI 20(R1),X'50'    USEREXIT called because of CI/CA split?
          BNE EXIT            No.  Return to VSAM
          MVI 21(R1),X'8C'    Tell VSAM that user wants to cancel split
          .
          .
          .
EXIT      .                   Nonstandard exit code -- restore R1 and
          .                   R14 from save registers
          BR R14              Return to VSAM which returns to USERPROG
                              if cancel is specified
          END                 End of USEREXIT