Logging Levels

Every logged event is categorized with one of a number of severity levels.

DEBUG or TRACE events provide low-level diagnostic information about the system, which can be used to assist in diagnosing a process or system that is not behaving as expected. DEBUG or TRACE events can generate high volumes of low level output, so is typically turned on and off as required.
INFO and AUDIT events provide information about what is happening on a normally running system. AUDIT events are those which you may wish to audit centrally, whereas INFO events are not expected to need central auditing.
SERVICE events are start and end messages from particular services.
WARN, ERROR or FATAL events provide warnings or errors about the system that need to be relayed to system administrators and/or users.