Kernel locks or file locks?

Hi, Sometimes a table gets locked up. We called informix and they said we needed to reboot the system to free up the locks, because we had kernel level locking. They said it was operating system dependant that determins whether we have file locks that can be easily removed or kernel locks which can only be removed by a reboot. I have never heard of such a thing. Is this true? Can I somehow switch to file level locking? Do I need to check with SUN? If it is true, is there anyway to get the locks released without rebooting? We have 50 - 100 users on the system at one time doing very time critical things. rebooting the system is not a good option. If it happens frequenty and can not be changed then we would look into switching DBs. This has not happened to often in the past but it happened twice in one week recently. We are running on a sun sparc solaris 2.2 with SE v5.0 and isql v4.0 or around there and esql v??. Any help would be appreciated. Thanks Bob Brass