another multi-user "solution"?

[Dan Shafer]

Rob....

Ah, good point. It would appear that there is not a simple way to solve 
this problem using text files as locking semaphores.

Back to the ol' drawing board!

On Apr 25, 2005, at 11:59 AM, Rob Cozens wrote:

> Hi Dan,
>
>> Second, using the semaphore file approach that Jacque suggested is 
>> eminently doable and quite simple to implement. It would be pretty 
>> easy, e.g., to have a single file that just contained a list of all 
>> the card numbers currently open for editing and checking it before 
>> allowing a user to edit a card's contents. Equally easy and perhaps a 
>> little better from a robustness perspective would be to create a text 
>> file called, e.g., card.lok, where card is the name or ID of the 
>> card, for a card when it's opened for editing and then deleting that 
>> file when the user's done. In either case, a pretty simple command 
>> could check to ensure the card the user asks to edit isn't already 
>> being edited and take some appropriate action.
>
> Question:
>
> How do changes on individual cards in different copies of a stack in 
> each user's RAM get made to the copy resident on disk?  There is not, 
> to my knowledge, a way to save changes on one card of a stack without 
> overwriting the entire stack.  So if I open a stack before you, 
> Jacque, and Kurt do, wait until you all close the stack, and then save 
> it, the only changes to the original stack will be mine.  You need to 
> take it the extra step the Rob Eppich took EPSI-Talk, and have each 
> users' copy of the stack updated whenever anyone else makes a change.  
> This was more feasible in HyperTalk than Transcript, me thinks.
>
> One advantage of a client-server design is record locking tables can 
> reside in the server's RAM; so no disk files are necessary and all 
> records are automatically unlocked when the server shuts down.
>
> Rob Cozens CCW
> Serendipity Software Company
>
> "And I, which was two fooles, do so grow three;
>  Who are a little wise, the best fooles bee."
>
>  from "The Triple Foole" by John Donne (1572-1631)
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>
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Dan Shafer, Co-Chair
RevConWest '05
June 17-18, 2005, Monterey, California
http://www.altuit.com/webs/altuit/RevConWest