A full SRF compile usually completes in under an hour for the standard Horizontal and Industry repositories. Many times developers report that a full SRF compile is very slow and is taking a significantly longer time.
The purpose of Siebel Audit Trail is to tracks changes to business component data made by users in the application, changes which are made through the Object Manager.
SRFDiff has been introduced in Siebel 8.1 and "Using Siebel Tools Version 8.1" > Chapter 12: Managing Repositories > Comparing Two Repository Files Using SRFDiff explains how to use it.
The .srf file is a compressed binary database. Siebel eBusiness Applications use compression techniques to optimize the size and performance of the .srf file at compilation time.
The only supported way in which you can delete a repository is by way of deleting the appropriate ‘Repository’ record within the Siebel Tools application.