File names.dat may be corrupt.

What is the question?

Assuming that you want this message to go away: you should run the analyze utility on the server that hosts your source safe installation. If it can't recover, you're in deep trouble and I hope you have a backup...

The dangers of using source safe is its unreliability and that it can easily corrupt itself. If that happens, it is very hard to recover. Source safe itself knows that it is unstable and requests that you run Analyze every month or so.

if I resotre from backup, it should keep version history.

have you tried, on the VSS server, the Analyze utility? That is quite harmless to use (it may not be able to recover, but it is worth a try).

If you have configured your backups properly, it should keep the version history. If your sysadmin has properly tested the backup configuration and its restore previously, it should be fine now to. If (s)he hasn't, then i'd recommend trying to restore to a different image first.

If you mean the backup functionality of VSS: it is just as unstable as VSS itself, but yes, it should keep the version history. Again: first make a full system backup before making any changes that may proof irreversible later.

Our sysadmin team just taking VSS Data folder backup with ntbackup utility. Does it keep version history if i restore VSS Data folder with ntbackup????

You still haven't tried the analyze util I suggested? Please do.

Yes, if all winds are blowing well, restoring the data directory would yield restoring history. But like I said again: VSS is a strange beast and you need quite some luck for this operation to succeed.

But, before you are going to blame me for giving the wrong advice and for loosing data: install VSS on a new server, and try to restore a backup there. If you manage that, you will also manage on your current server.

and... read the section on "Finding and Repairing Data Corruption" in that same article. It may be a life saver for you.