Part III: More-Advanced Access Techniques
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updates to records in a database. Access security, on the other hand, prevents unauthorized users
from viewing or changing not only the data, but the database objects such as forms and reports.
Hand in hand, record locking and security combine to ensure the integrity of the application and
its data.Note
Access security was removed from the .accdb file format. It is, however, still available if you continue to use
the .mdb file format.
Note
Some of the examples in this chapter are given using both ActiveX Data Objects (ADO) and Data Access
Objects (DAO) syntax. Although ADO is superior to DAO for some purposes, many Access developers spend
time maintaining applications written with DAO code. Because proper handling of multiuser issues is so impor-
tant in many environments, I felt it was necessary to show both the proper ADO and DAO code involved with
record locking.
Working on a Network
Multiuser applications require a network of some kind. Generally, the type of network you use
doesn’t matter. Multiuser issues are the same regardless of the underlying networking technology.
The speed of your network, the location of your application’s files, and the type of data source that
you’re accessing are all important considerations when planning your network installation.
Although I’ve listed these as three separate items, they’re all related to the fundamental issue of
database performance.No matter how well it’s written, if your application performs poorly due to network bottlenecks,
the application will get the blame, not the network.Network performance
When you develop applications in Access, a good rule of thumb is to always plan for the lowest
common denominator — that is, write your database applications as if they were going to be used
on the most minimally equipped computer possible. Preparing databases that will be used in net-
worked environments is no different. There are many different network topologies and speeds out
there — everything from remote-access dial-up lines running on slow modems to megabit net-
works and dedicated T1 lines.Tip
Plan ahead: If you’re writing an application that will be used in a high-speed, low-traffic network environment,
you can afford to be a little extravagant and less stringent in your control of record-locking issues. But if your
application will be used by traveling salespeople dialing in over phone lines to retrieve customer and order
information, your approach should be very conservative, and your design will have to accommodate the fre-
quent updates that are likely in this scenario.