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  1. #1
    Join Date
    Oct 2003
    Posts
    6

    Red face Unanswered: Difficult Multi User Question ? ! ?

    Thanks for all the replies guys these forums are great and its wonderful having access to your knowledge.

    We are using a VB 6 frontend connecting to a MS Access Database which is the backend.

    How is it possible to have a real time point of sale system without running into locking problems ??????

    If you have the main database which is storing your stock for example and you have two client PCs selling items and taking information out of the database how will it be possible for them to sell the same items at the same time and not get a lock problem. Say both clients sell a coca cola and log store the sale. You will get a locking problem right ??

    I have no idea how to get around these locking issues. Multi user database is basically impossible with locking as far as I can see ?

  2. #2
    Join Date
    Oct 2003
    Posts
    78
    The first thing that comes to my mind is, why do you want to do away with locking issues? Locking issue is very important while updating the database. Take your example. Lets say there are only 10 coca colas. Merchant A wants to sell 9 and Metchant B wants to sell 8. Considering the number of coca colas, one merchant must get the lock to sell the desired number of drinks. If lock will not be there, then both will be able to sell 9+8=17 drinks, when in reality there are only 10 drinks.
    I know this is not exactly the answer to your question, but I thought it worth while to post as a suggestion. Hope this helps....!! Cheers.

  3. #3
    Join Date
    Oct 2003
    Location
    Jordan
    Posts
    28
    Hi all


    As in the previous post record lockes are very important. every time you request an item Like COCA COLA your should check quantities on hand. in a multiuser environment when accessing this information you should :

    first check if the record is locked by another user if so wait until freed
    when the record is free lock it
    do your calculations
    unlock the record

    Again you can have the same issue in POS systems. try using temporary tables for each point or user.


    Regards,



    ________________
    Firas arramli
    SEI Systems Analyst

  4. #4
    Join Date
    Oct 2003
    Posts
    6

    Unhappy Temporary Tables

    All our clients on the current system are using temporary tables on each client. the server's database only gets updates when the client logs off, this is causing us a problem because the server should have realtime information of all stock. ie. they should be updating the server after each sales instead of after the client logs out for the day.

  5. #5
    Join Date
    Nov 2003
    Posts
    150
    Any progress on this??

    I'm planning on deploying a very similar system, and i'm still not sure about a few details.

    cheers!
    Cheers!

    Mr.Crud

    There are 10 kinds of people, ones that understand digital, others that dont

  6. #6
    Join Date
    Feb 2002
    Posts
    2,232
    What type of driver will you be using ado or dao ? Basically, you will have to determine the level of concurrency that is acceptable to your application - pessimistic or optimistic.

  7. #7
    Join Date
    Aug 2003
    Location
    Argentina
    Posts
    465
    The problem with locking is when you use the method add or update, but with an appropriate politics of lock ( pessimistic or optimistic ) you can drive very well the problem.
    Saludos
    Norberto

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