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 arenot compatible with those of the streams that have already been allowed entry tothe file.On OpenVMS, Table 8–1 shows the valid and invalid OPEN ALLOWINGcombinations between first and subsequent access streams. (The subsequenttable is the equivalent for Tru64 UNIX systems.) The table assumes no fileprotection violations on the first stream.Table81 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 G3 2G3 25
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 GG 2GG 25
INPUT
READERS 44 2GG 25
INPUT
NONE 1 1 1,2 1 1 1,2 5
OUTPUT
ALL G3 2G3 25
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
GSecond stream successfully opens and file sharing is granted.
1Second stream is denied access to the file because the first stream requires
exclusive access (the first stream specified NO OTHERS).
2Second stream is denied access to the file because the second stream
requires exclusive access (the second stream specified NO OTHERS).
810 Sharing Files and Locking Records