When you use Grid API functions, you must call the initialization function, EssGInit. This function performs the following tasks:
Passes information about your environment to the Grid API functions.
Provides you with an instance handle that you use for future communication with the Grid API functions.
When you call EssGInit, you get the Grid instance handle. If you want to use regular API functions, you can use EssGGetAPIInstance to get the API instance handle and EssGGetAPIContext to get the login context handle. See Using the C Main API Functions.
You cannot use Main API instance handles and login contexts in Grid API calls. See Using the C Main API Functions.