The list of options for extending SID caching functionality can become quite long so an external SID cache API was created for those who are more discriminating about managing SID cache data. There are several callbacks used for external SID cache access.

Note that there are probably few applications where using an external SID cache makes sense. Some suggested environments where it might be considered is in a server configuration where multiple instances of a server exist for workload balancing purposes. It might be desirable to have a single SID cache to be used by all of the processes which each server is running in. Usually this can be avoided by writing applications which are multi threaded. All threads would use the single internal SID cache buffer.