By using the basic indexed sequential access method (BISAM) to process an indexed sequential data set, you can directly access the records in the data set for:

• Direct retrieval of a record by its key
• Direct update of a record
• Direct insertion of new records.

Because the operations are direct, there is no anticipatory buffering. However, if ‘S’ is specified on the READ macro, the system provides dynamic buffering each time a read request is made. (See Figure 1.)