Sequential Files

Files with sequential organization can be accessed only sequentially. The sequence in which records are accessed is the order in which the records were originally written.

X Line Sequential Files

X Same as for sequential files (described above).

Indexed Files

All three access modes are allowed.

In the sequential access mode, the sequence in which records are
X accessed is the ascending order (or optionally under AIX, OS/2, and
X Windows, descending order) of the record key value. The order of retrieval within a set of records having duplicate alternate record key values is the order in which records were written into the set.

In the random access mode, you control the sequence in which records are accessed. The desired record is accessed by placing the value of its key(s) in the RECORD KEY data item (and the ALTERNATE RECORD KEY data item). If a set of records has duplicate alternate record key values, only the first record written is available.

In the dynamic access mode, you can change, as necessary, from sequential access to random access, using appropriate forms of input-output statements.

Relative Files

All three access modes are allowed.

In the sequential access mode, the sequence in which records are
X accessed is the ascending order (or optionally under AIX, OS/2, and
X Windows, descending order) of the relative record numbers of all records that currently exist within the file.

In the random access mode, you control the sequence in which records are accessed. The desired record is accessed by placing its relative record number in the RELATIVE KEY data item; the RELATIVE KEY must not be defined within the record description entry for this file.

In the dynamic access mode, you can change, as necessary, from sequential access to random access, using the appropriate forms of input-output statements.

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