ClearCase is a version file system masquerading as project version control. It's heavyweight, clumsy, and brittle, and it's easy to get yourself in an inconsistent state.<p>At one enterprise in my past it could take months to merge for release, during which time the entire repository was locked for everyone. I suspect it was the 30 years of commit history. It took years to move to something more modern.<p>Much better than Microsoft [Visual] SourceSafe.