The database server process or thread with which your application program was working has terminated. The DBA might have shut the system down. The next most likely cause is an internal error. Look for operating-system messages that might give more information. If the error recurs, note all circumstances and contact IBM Informix Technical Support.
Check the ISAM error code that is returned with this error. If it is -129, the database server has not terminated but simply reached a limit on the number of concurrent user sessions (see the explanation of error -129).