Multiple modules(units) means multiple units in the application. Only one module can be active at one time. The others will be saved and displayed as inactive. Note that if dbMultiModules = false (default) and there are multiple modules (unit), then they will be executed in a serial manner. There are 2 types of multi-modules - Stand alone modules - This type of modules demands a clean variables reset. Use dbUnit=xxx_New if needed.Master / Slave modules.
There is also a requirement for MultiModules - Display must use ASPdbSendTemplate. When dbMultiModules=True, the modules will have no display but instead the display is saved in Session("ASPDB_SAVE_Unit"). All the 'modules' must be displayed using the ASPdbSendTemplate method.If you are using calendar, validator or any Applets with multiple instances you must disable all except the active module to avoid duplicate declarations. The easier way is to detect the active unit number and then comment out the properties.