The Web Application Server comes bundled with some cartridges. Each cartridge is independent of one another. If a cartridge fails, other cartridges and components in the Web Application Server are not affected. A cartridge instance is a process for a cartridge. You usually have multiple cartridge instances for each cartridge type.
Instances can run on different machines on the network.
Cartridge Architecture Cartridges are built using the WRB API, which allows them to access WRB system services, and contain a copy of the WRB execution engine. Cartridge architecture Initialize , Exec , and Shutdown are callback functions defined in a cartridge. These functions are called when the cartridge is started up, handles a response, or shuts down. See Callback Functions in a Web Cartridge for a list of callback functions. Using the WRB API, you can build your own cartridges as well.