Compaq COBOL AAQ2G1FTK - Manual (Page 262)

Sharing Files and Locking Records
8.3 Ensuring Successful File Sharing
a file is shared. Note that some streams can be locked out if their intentions are
not compatible with those of the streams that have already been allowed entry to
the file.
On OpenVMS, Table 8–1 shows the valid and invalid OPEN ALLOWING
combinations between first and subsequent access streams. (The subsequent
table is the equivalent for Tru64 UNIX systems.) The table assumes no file
protection violations on the first stream.
Table 8–1 File-Sharing Options (OpenVMS)
FIRST STREAM SUBSEQUENT STREAM
Open mode:
Allowing: UPDATE
ALL UPDATE
READERS UPDATE
NONE INPUT
ALL INPUT
READERS INPUT
NONE OUTPUT
ALL
READERS
NONE
UPDATE
ALL G 3 2 G 3 2 5
UPDATE
READERS 4 3,4 2 G 3 2 5
UPDATE
NONE 1 1,3 1,2 1 1,3 1,2 5
INPUT
ALL G G 2 G G 2 5
INPUT
READERS 4 4 2 G G 2 5
INPUT
NONE 1 1 1,2 1 1 1,2 5
OUTPUT
ALL G 3 2 G 3 2 5
OUTPUT
READERS 4 3,4 2 G 3 2 5
OUTPUT
NONE 1 1,3 1,2 1 1,3 1,2 5
Legend
UPDATE OPEN EXTEND or OPEN I-O
INPUT OPEN INPUT
OUTPUT OPEN OUTPUT
ALL ALLOWING ALL or ALLOWING UPDATERS or ALLOWING WRITERS
READERS ALLOWING READERS
NONE ALLOWING NO OTHERS
G Second stream successfully opens and file sharing is granted.
1 Second stream is denied access to the file because the first stream requires
exclusive access (the first stream specified NO OTHERS).
2 Second stream is denied access to the file because the second stream
requires exclusive access (the second stream specified NO OTHERS).
8–10 Sharing Files and Locking Records