Security Audit Questions

I am going going through a security audit and I have been asked to participate in documenting a threat model for the Commvault deployment. I need some help documenting the  order of events when a backup is initiated  and which entity is initiator and responder in the process.  I am having trouble finding this in the documentation. Hoping someone can point me to the documents, or has insight into the sequence of events in a backup.

I need to document Agent based and VSA  snapshots 

Thanks