Hi George,
If I have a NFS mounted directory (on a third non-UV system)
which houses a UV format file.
I have (2) linux system that have that directory mounted, which
each have UV that have a VOC pointer to that file. <1>F ,
<2> /mnt/directory/filename ,
<3> /mnt/directory/D_filename
Both UV systems can read/write to this file, but only one system
will be writing to the file, the other will only be reading.I realize
locking is not respected from one system to another.
Be careful! I have seen (and repaired) files that have been damaged in
broadly similar situation.
As you say, the locking system will not work as the file is being accessed
by two completely independent UV systems. The problem that you may have is
not with record locking but with group locking that protects the internal
structure of the file. Even with only one system writing, it is possible
(likely?) that there will be times when the system doing the reading will
access a group at the same moment that the other system is modifying an
overflow chain.
If I defined a trigger on this file on the system that will only be
doing the reading, will it detect any changes to the file when the
other UV makes changes?
No. Triggers are fired somewhere deep in the UV file system. There is no way
in which one system can know about changes applied by the other system.
Even with uv/net to avoid the locking problems, the triggers are not going
to get run on both systems for an update.
Basically System1 will be making changes to that file.
And System2 will need to update on it's system based on those
changes.
Sounds like you need to investigate data replication, changing the network
structure if necessary.
Martin Phillips
Ladybridge Systems Ltd
17b Coldstream Lane, Hardingstone, Northampton, NN4 6DB
+44-(0)1604-709200
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