This function is called by a server that can register multiple class objects to inform the OLE SCM about all registered classes, and permits activation requests for those class objects.
Servers that can register multiple class objects call CoResumeClassObjects once, after having first called CoRegisterClassObject, specifying REGCLS_LOCAL_SERVER | REGCLS_SUSPENDED for each CLSID the server supports. This function causes OLE to inform the SCM about all the registered classes, and begins letting activation requests into the server process.
This reduces the overall registration time, and thus the server application startup time, by making a single call to the SCM, no matter how many CLSIDs are registered for the server.
Another advantage is that if the server has multiple apartments with different CLSIDs registered in different apartments, or is a free-threaded server, no activation requests will come in until the server calls CoResumeClassObjects.
This gives the server a chance to register all of its CLSIDs and get properly set up before having to deal with activation requests, and possibly shutdown requests.
To determine whether the platform supports this function, see Determining Supported COM APIs.