I/O feedback area

The system updates the I/O feedback area for every successful I/O operation unless your program uses blocked record I/O.

In that case, the system updates the feedback area only when it reads or writes a block of records. Some of the information reflects the last record in the block. Other information, such as the count of I/O operations, reflects the number of operations on blocks of records and not the number of records. See your high-level language information to determine if your program uses blocked record I/O.

The I/O feedback area consists of two parts: a common area and a file-dependent area.