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

• QSAM processes all record formats except blocks with keys.
• QSAM blocks and unblocks records for you automatically.
• QSAM manages all aspects of I/O buffering for you automatically. The GET macro retrieves the next sequential logical record from the input buffer. The PUT macro places the next sequential logical record in the output buffer.
• QSAM gives you three transmittal modes: move, locate, and data. The three modes give you greater flexibility managing buffers and moving data.