Microsoft Access Database Architecture: Storing Temporary Data and User Settings

Users are annoyed to re-enter their last specifications when the application should start with that as its default. After all, computers are supposed to remember things, right?

At the simplest level, the user's settings and can be stored in memory as global variables in VBA or TempVars. These are temporary and disappear when the application closes. However, while it's open, the program can default to those values when they should be reused.

Temporary variables and TempVars can also be used and referenced via macros.

Another way to save user preferences is to store it in the user's Windows registry. This lets you store data on a machine specific to the user for your application. It's not appropriate for saving large amounts of data that should be in a table but helpful for user selections. VBA offers a few simple commands to manage registry settings:

• GetSetting(appname, section, key[, default])
• SaveSetting appname, section, key, setting
• DeleteSetting appname, section[, key]

If you define your application name and where to store the values, you can create, retrieve, and delete your values there. Once you load them into your variables, you can apply them as you would any global variable. You'll need to make sure you define your application name to not conflict with others.

Issues with Storing Data in the Registry

If you have a front-end/back-end split database design, storing values in the registry lets you update your front-end database without losing the user's selections.

Of course, registry settings are only stored on that machine. If the user runs your application on another machine, these settings do not exist there. If this is important, the settings should be saved in tables in the back-end database for each user, then loaded when they log-in.

32 and 64 Bit Support

Note that these functions work in all versions of Microsoft Access including 32 and 64-bit versions of Access 2010 and later.

For more advanced code using Windows API commands to manage registry entries, check our our Windows Registry VBA code in Total Visual SourceBook.

A nice thing about databases is that tables are available to store data and lots of it.

Split Database Design with Temporary Tables in the Front End

Tables can be used to save more data and may be preserved either locally or centrally. With a split-database Microsoft Access architecture where the application front-end database is linked to the shared back-end database, allows the front-end database to contain tables that are private to each user. It also supports multi-user environments without collisions.

Temporary tables can also be located here if multiple steps are necessary to complete a process, a complex report that requires multiple aggregations and selections for example. For more information about split database architecture, visit Splitting Microsoft Access Databases to Improve Performance and Simplify Maintainability

For SQL Server applications, one can use tables that are private to each user. These tables may be emptied each time the process is finished or when the application closes, or remain untouched to be available the next time the user is in the same section.

The nice thing about using tables to store user selections is that it's automatically preserved the next time the program is run. For instance, you may have a selection screen to find some data. If that form is bound to a table that's local to the user, the next time the form is opened, the last selections are preserved. No programming is required.

However, these settings disappear if a new version of your application is deployed that replaces the user's front-end copy of your database.

Anticipate that if your application is updated, you need to make sure any previously saved settings are appropriate. For instance, if your previous version allowed saving a selection that is no longer valid, you'll need to make sure that doesn't cause a problem in your new version from a data validation or security perspective.

If that is a concern, storing the data in the front-end database and deleting or resetting the values when a new version is deployed ensures previous values are not used.