Checkpoints problems

Hi A friend of mine is running informix online 5.01 ud3 in aix 3.2.5. The workstations are running inet 5.01 and q+e odbc library. At some time (generally during heavy load), users begin to complanit that they can't connect to the database server. But logged users still works fine. Some time later even logged users can't continue working. If as informix you try to do a backup, you can't. tbmonitor complaint that there is a checkpoint in process. Viewing the online log there are 80000 lines of the following message (1 hour of log): Process Aborted Abnormally: pid=NNNN user=NNNN us=NNNNN flags=XXXX If you extract only unique lines (without considering the hour) you get only 154 lines. It seems that they are retries of the same users. In fact you have 3 lines per user with different flags. My questions are: Is there any place where I can find how to decode the hex flags into something readable ? Does someone have any idea of what is causing such behaviour of a checkpoint ? I couldn't find the error message in the online administrator manual. All the messages related to "Process ..." have a qualifier of what were doing the process (commit, rollback, ...) Does someone have any idea of where I can find the explanation of this error message ? Thanks in advance Javier