In this example, the ACB macro is used to identify a data set to
be opened and to specify the types of processing to be performed.
The access method control block generated by this example is built
when the program is assembled.
BLOCK ACB AM=VSAM,BUFND=4, BLOCK gives symbolic x
BUFNI=3, address of the access x
BUFSP=19456, method control block. x
DDNAME=DATASETS, x
EXLST=EXITS, x
MACRF=(KEY,DIR,SEQ,OUT), x
STRNO=2
The parameters of the ACB macro follow:
- BUFND specifies four I/O buffers for data. BUFNI specifies three
I/O buffers for index entries. BUFSP specifies 19456 bytes of buffer
space, enough space to accommodate control intervals of data that
are 4096 bytes and control intervals of index entries that are 1024
bytes.
- DDNAME specifies this access method control block is associated
with a DD statement named DATASETS.
- EXLST specifies the exit list associated with this access method
control block is named EXITS.
- MACRF specifies keyed-direct and keyed-sequential processing for
both insertion and update.
- STRNO specifies two requests will require concurrent positioning.
- Since the type of resources are not specified, NSR is assumed.