ClearCase is far and away one of the most reliable version control repositories in the industry. But repository corruption does indeed happen. I had a situation where the ClearCase vob got corrupted when we were using a NAS repository for storage. We actually recreated the problem outside of ClearCase by just writing some files. The problem turned out to be a CIFS (e.g. windows) configuration issue on the NAS device itself. The problem actually had nothing to do with ClearCase.
There are five utilities used to check the integrity of the vob repository. checkvob should be run each night. I haven't used Clearcase in a few years so I am forgetting the names of the other utilities but I think checkdb (or is it dbcheck) verifies the underlying rama database.
What you really need to do is to move from using one monolithic ClearCase vob to a using bunch of vobs. Since you can script your administration commands having many vobs is just as easy to maintain as having only one or two. (Actually easier because you will have fewer problems)
My scripts would iterate over a list of vobs (excluding a couple of test vobs). Even with a corrupt vob you can often get out history for a specific slice of the vob (or get IBM to help you the use vob_splitter utility).
I used to periodically reformatvobs just to ensure that that they were ok and I setup a separate ClearCase registry on a separate machine to do this (you cannot use a copy of a vob in the same registry because the uuids will conflict).
You will see fewer problems with smaller vobs (even if you have a lot of them). We literally had hundreds of vobs and ran checkvob every night. I am knee deep in implementing RTC, TFS and Git but ClearCase still rocks!
Feel free to connect with me on linkedin or ping me via email ([email protected]) to discuss further and do post how this all works out!
Bob Aiello, Technical Editor CM Crossroads