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. The caller requests that the VSAM control blocks and I/O buffers be obtained above 16 megabytes, if possible.

BLOCK2   ACB   AM=VSAM,                   BLOCK2 gives symbolic         x
               DDNAME=DATASETS,           address of the access         x
               EXLST=EXITS,               method control block.         x
               MACRF=(KEY,DIR,SEQ,OUT),                                 x
               RMODE31=ALL

The ACB macro's parameters are:

• 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.
• RMODE31=ALL specifies both VSAM control blocks and buffers may reside above 16 megabytes.
• Since the type of resources are not specified, NSR is assumed.