For identification and filtering purposes, events logged by all CMS-supported services are classified into various categories. These are listed in Table 25.3. Each category represents messages that are of the same or a similar nature or that belong to a specific functional area. A particular log, for example the error log, can record entries that fall under one or more of these categories.
In the CMS configuration, each message category corresponds to a specific log
level. Log levels are represented by numbers (digits) 1 to 6, each digit
indicating the level of logging to be performed by the server--that is, how
detailed the logging should be.
You can use log levels to filter log entries based on the severity of an event. By default, a level 3 (Failure) is set for all services.
Important
The log level is additive--that is, specifying a value of 3 causes levels 4, 5, and
6 to be logged. Log data can be voluminous, especially at lower (more verbose)
logging levels. Make sure that the host machine has sufficient disk space for all
the log files. It is also important to define your logging level, log rotation, log
expiration, and server-backup policies appropriately so that all the log files are
backed up and the host system doesn't get overloaded; otherwise, you may
lose information.
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