Demand loading is a feature of AutoCAD that automatically attempts to load an ObjectARX application that is not resident in AutoCAD. ObjectARX applications can be designed for loading by AutoCAD under one or more of the following circumstances:
- When a drawing file that contains custom objects created by the absent application is read
- When a user or another application issues one of the absent application's commands
- When AutoCAD is started
Autodesk recommends developing ObjectARX applications that take advantage of AutoCAD's demand-loading feature because demand loading provides the following benefits:
- Limits the creation of proxy objects (see Proxy Objects)
- Provides greater flexibility for loading ObjectARX applications
- Conserves memory by loading applications only when their functionality is required
For an application to be accessible for demand loading, application-specific information must be present in the Windows system registry. In addition, ObjectARX applications with more than one DLL may need a “controller” module that is responsible for loading all other components of the application. Finally, the DEMANDLOAD system variable must be set to the appropriate value for demand loading.
An ObjectARX application can be demand loaded from a path on the local machine, or by using an Internet address.