Chapter 10. Multiuser Applications

Access offers native support, right out of the box, for multiuser applications. But this additional power brings with it some additional problems, chiefly those of coordinating multiple users who may be spread across a large network. This chapter explores some solutions to common problems in multiuser applications. You'll learn how to use a shared database table to help your users communicate with one another and see how to find out which users are logged in at any given time. You'll also learn how to implement basic transaction logging, how to determine who has a record locked, and how to prevent a user from locking a record for an excessive time period. Because multiuser applications often use Access security, we also explore the security system in detail. For instance, you'll learn how to properly secure your database, how to keep track of your users and groups, and how to check if they have blank passwords. You'll also see how you can maintain separate but synchronized copies of a database using Access replication.

Several of the examples in this chapter take advantage of the DAO type library, rather than the default ADO library used by Access 2002 and Access 2003. Even though it's less "modern," DAO provides greater functionality, and generally better performance. In addition, using DAO makes it possible for these demonstrations to work in earlier versions of Access. If you want to try these techniques in your own applications, make sure you add the DAO reference to your project using the Tools References menu item from within VBA—it won't be added by default.