Read when logical file shares an access path with more keys operation

When the first-in-first-out (FIFO), last-in-first-out (LIFO), or first-changed-first-out (FCFO) keyword is not specified in the data description specifications (DDS) for a logical file, the logical file can implicitly share an access path that has more keys than the logical file being created.

This sharing of a partial set of keys from an existing access path can lead to perceived problems for database read operations that use these partially shared keyed sequence access paths. The problems might appear to be:

Records that should be read, are never returned to your program
Records are returned to your program multiple times

What is actually happening is that your program or another currently active program is updating the physical file fields that are keys within the partially shared keyed sequence access path, but that are not actual keys for the logical file that is being used by your program (the fields being updated are beyond the number of keys known to the logical file being used by your program). The updating of the actual key fields for a logical file by your program or another program has always yielded the above results. The difference with partially shared keyed sequence access paths is that the updating of the physical file fields that are keys beyond the number of keys known to the logical file can cause the same consequences.

If these consequences caused by partially shared keyed sequence access paths are not acceptable, the FIFO, LIFO, or FCFO keyword can be added to the DDS for the logical file, and the logical file created again.