Information
The FortiGate system memory has a limited capacity and displays only the most recent log entries. Traffic logs are not stored in the memory buffer, due to the high volume of traffic information. After all available memory is used, by default, the FortiGate unit begins to overwrite the oldest log messages. All log entries are deleted when the FortiGate unit restarts.
Solution
To set the full-final-warning-threshold, use the following command:
config log memory global-setting
set full-final-warning-threshold 95
end