The following log levels are used. They are chosen based on the idea that it should be easy for the system administrator to find out, whether any action on his part is needed.
| DBG | debug message | Debugging messages. Generally, these are only interesting for the developer. A system administrator might enable them to help the developer finding bugs. |
| INF | informational message | Informational messages produced while the program runs its normal course. They are mainly used for statistics and to show what the program has been doing. |
| ERR | error message | Messages which denote an error in the normal course of the program. These might be messages like 'password mismatch', i.e. errors based on user input. An ERR message is normally not a concern for the system administrator, but it might be for customer support personnel. ERR messages have an extra label, because they can be found more easily that way. A very high number of ERR messages might indicate a system problem in another part of the system, like database corruption or network problems. The ratio of INF to ERR messages is probably a good indication of those kinds of problems. |
| ADM | admin intervention required | These messages denote things that need attention by the system administrator. They might signal if the system is near an overload condition etc. The system administrator should inspect those messages regularly and act on it. These messages are not really time critical, maybe they are only a warning that new hardware should be installed, or they might warn of data corruption in one users mailbox. Lots of these messages in a short time frame might indicate a critical situation. |
| SOS | critical event | These messages denote critical system events like system or disk overload, processes crashing, etc. Generally, they demand an immediate intervention by the system administrator, although the system might try to keep running. |
| BUG | software bug | These messages are produced by internal assertion code and denote system states that are not supposed to happen. This probably means there is a bug in the program or something else happens, that the developer didn't anticipate. These messages should be reported to the developer. |