Strange 'iserrno' returned under CISAM

I have recently run into problems with a system running an application that utilizes Informix C-ISAM 3.10. As a background, our application has been running on a DEC 5000/200 platform for approx. one year under a fairly consistent load condition without the problem that I am about to describe. We have a file that is used to catch all C-ISAM errors from the application and until a month ago this file went largley unused. Now after approx. 24 hours of operation the file is filling up with errors that are related to this C-ISAM call: < cc = isread(fd, buff, mode) > This call is returning a -1 and the resulting iserrno equals 28. I understand that this is an Ultrix error equivalent to "no space left on device" but I don't see how it is possible. All file system partitions are at 50% or less of allocated size. What device would it be referring to and is there a compelling reason why this would be popping up now? Jim Welch (welch@mdd.comm.mot.com)