Access 2003 VBA Programmer's Reference

17.1. ADP Versus MDB: Choosing the Right Client Format

Many misconceptions exist regarding the differences between an Access project (ADP) and regular Access database (MDB). Even before ADP files were available starting with Access 2000, many developers did not fully understand how MDB files worked or how to optimize their usage in a client/server environment. While even serious design mistakes can still provide acceptable performance with only a few simultaneous users, as applications grow the effects of inefficient application design can have serious detrimental effects on performance and reliability.

17.1.1. What Is an MDB File?

Although it is quite common to refer to MDB files as Access databases, it is more accurate to call them Jet (Joint Engine Technology) databases. Microsoft Access uses the Jet database engine to create and manage MDB files. Although Access is the most common application used for creating and managing them, you can create Jet databases without ever installing or using Access itself (by using Microsoft Visual Basic, for example).

A traditional Access database uses the Jet database engine to store all data, forms, code, and properties associated with your application. Starting with Access 2000, all nondata objects are stored in a single record of a database system table used by Access. When Access goes to open an MDB file, it searches for this record and loads the VBA project and any objects that are needed by your application.

17.1.1.1. Linking to External ...