Example 3: skip-sequential retrieval (KSDS, variable-length RRDS)

In this example, a GET macro is used to retrieve variable-length records synchronously. Records are processed in the I/O buffer. The search argument is full key, compared greater-than-or-equal; key length is 8 bytes.

The records are retrieved in key sequence, but some records are skipped. Skip-sequential retrieval is similar to keyed-direct retrieval, except that you must retrieve records in ascending sequence (with skips) rather than in a random sequence.

If the data set is a variable-length RRDS, specify the relative record number in the ARG field, and the record length in the RECLEN field in the RPL.

        GENCB  BLK=ACB,          VSAM gets an area in virtual storage   x
               DDNAME=INPUT,     to generate the access method control  x
               MACRF=(KEY,       block and returns the address in       x
               SKP,IN)           register 1.
 
        LTR    15,15
        BNZ    CHECK0
        LR     2,1
        GENCB  BLK=RPL,                                                 x

               ACB=(2),                                                 x
               AREA=RCDADDR,                                            x
               AREALEN=4,                                               x
               ARG=SRCHKEY,                                             x
               OPTCD=(KEY,SKP,                                          x
               SYN,NUP,KGE,                                             x
               FKS,LOC)
        LTR    15,15
        BNZ    CHECK0
        LR     3,1               Address of the request parameter list.
        .
LOOP    MVC    SRCHKEY,source    Search argument for retrieval, moved in
                                 from a table or a transaction record.
        GET    RPL=(3)
        LTR    15,15
        BNZ    ERROR
        SHOWCB AREA=RCDLEN,      Display the length of the record.      x
               FIELDS=RECLEN,                                           x
               LENGTH=4,                                                x
               RPL=(3)
 
        LTR    15,15
        BNZ    CHECK0
        .
        B      LOOP
ERROR   ...                      Request was not accepted, or failed.
CHECK0  ...                      Generation or display failed.
        .
RCDADDR DS     F                 Work area into which VSAM puts the     x
                                 address of a data record within the    x
                                 within the I/O buffer (OPTCD=LOC).
 
SRCHKEY DS     CL8               Search argument for retrieval.
 
RCDLEN  DS     F                 For displaying variable record lengths.

The macros and instructions are as follows:

The first GENCB generates an access method control block, which specifies keyed, skip-sequential, and input processing. The address of the access method control block is stored in register 2.
The second GENCB generates a request parameter list. The address of the request parameter list is stored in register 3.
MVC moves the search argument into SRCHKEY, the area defined for the search argument.
GET specifies that the record pointed at by the request parameter list whose address is in register 3 is to be retrieved. Records are retrieved by a skip-sequential search through the sequence set of the index.