When you use BSAM to process a sequential data set and members of a PDS or PDSE, the following rules apply:

• BSAM can read a member of a PDSE program library, but not write the member.
• The application program must block and unblock its own input and output records. BSAM only reads and writes data blocks.
• The application program must manage its own input and output buffers. It must give BSAM a buffer address with the READ macro, and it must fill its own output buffer before issuing the WRITE macro.
• The application program must synchronize its own I/O operations by issuing a CHECK macro for each READ and WRITE macro issued.
• BSAM lets you process blocks in a nonsequential order by repositioning with the NOTE and POINT macros.
• You can read and write direct access storage device record keys with BSAM. PDSEs and extended-format data sets are an exception.
• BSAM automatically updates the directory when a member of a PDS or PDSE is added or deleted.