The bdump and cdump directories are database parameters. Look at v$parameter to see where they point, just be aware that you need to query with lower case letters for that view. Do you do a cold backup of the database? If so are you getting errors restarting the database? Is someone doing a shutdown abort? Is the backup job doing a hot backup, but locking the datafiles? If you do a hot backup you need to put each tablespace into backup mode before you back up its datafiles. This is especially important on Windows machines. How do you do your backups?