I have a service that produces a lot of event log output. Currently the event log is configured to overwrite any old events to keep the log from ever getting full. We have also increased the event log size considerably (to about 600 MB). Recently the service started reporting errors to its clients, and the error message it was sending to its clients is "The event log file is full". How can this be, when event log is configured to overwrite as necessary? In our hurry to get the service back up we cleared the event log without saving its contents, but most likely it had not reached 600 MB yet, judging from sizes of some earlier log dumps. There is also MS KB entry 312571, which reports that a hot fix to a similar issue is available, but the the configuration that the fix applies to is not exactly the same we have. Specifically, the fix only applies if event logs are configured to never overwrite old events. I wonder if this has something to do with the fact that the log files apparently are memory-mapped. What happens if the system runs out of address space to map files to?