Chapter 13 Logging and Reporting : Troubleshooting and logging : Connection issues between FortiGate unit and logging devices : FortiGate unit has stopped logging
  
FortiGate unit has stopped logging
If the FortiGate unit stopped logging to a device, test the connection between both the FortiGate unit and device using the execute ping command. The log device may have been turned off, is upgrading to a new firmware version, or just not working properly.
The FortiGate unit may also have a corrupted log database. When you log into the web-based manager and you see an SQL database error message, it is because the SQL database has become corrupted. View “SQL database errors” in the next section before taking any further actions, to avoid losing your current logs.