The error logging daemon, syslogd, automatically records various system warnings, errors, and faults in message files. These messages can alert you to system problems such as a device that is about to fail.
The /var/adm directory contains several message files. The most recent messages are in the /var/adm/messages file. After a period of time (usually every ten days), a new messages file is automatically created. The original contents of the messages file are rotated to a file named messages.1. Over a period of time, the messages are further rotated to messages.2 and messages.3, and then deleted.