I know I've said it many times, but I'll say it again... there just isn't enough information in your post for us to determine the problem.
Help US to help YOU by making it easy for us to understand the problem. Describe the versions of CMOD, DB2, and Operating System at a minimum. Tell us what you've investigated or tried to fix the problem, and what the result was.
Show us your configuration, especially storage management. And there is usually an error in the system log when there's a failure of any kind, so a screen shot of the System Log would be nice too.
Until then, there's very little we can say, other than "check everything".
-JD.