Richard,
I think I need to learn about semaphores! Any suggestions for a good
tutorial?
One of the things we want to do is exclude locked records from a query.
Will semaphores provide for that?
Thanks!
- Ron
On 1/27/2010 8:14 AM, Richard Quadling wrote:
The technique I've used in the past is semaphore locking, where the
semaphore contains the session and the expected expiry time.
Follow this.
User a starts the process of editing a record.
Set the semaphore where there is :
a - no existing semaphore - no ongoing edits.
b - the semaphore's session is the same - repeat edits by this user
in the same session (expired or otherwise).
c - the semaphore has expired - the other user simply took too long.
If the semaphore cannot be set it will be because of :
d - Different non expired session - someone else is editing the record.
When a user saves the row, you just remove the semaphore.
The semaphores could be in a separate table (rather than on the record itself).
Different tables have different number of columns so take different
amounts of time to edit, so each table would have a different amount
of time from edit to expiry.
An entry on a lookup table (just a description) should, in the main,
be completed within 30 seconds.
But a detail line for a purchase order may take several minutes.
You'll have to tune this to your own needs.
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