As with any system, FortiOS has a finite set of hardware resources such as memory and all the running processes share that memory. Depending on their workload, each process will use more or less as needed, usually more in high traffic situations. If some processes use all the available memory, other processes will have no memory available and not be able to function.

When high memory usage happens, you may experience services that appear to freeze up and connections are lost or new connections are refused.

If you are seeing high memory usage in the System Resources widget, it could mean that the unit is dealing with high traffic volume, which may be causing the problem, or it could be when the unit is dealing with connection pool limits affecting a single proxy. If the unit is receiving large volumes of traffic on a specific proxy, it is possible that the unit will exceed the connection pool limit. If the number of free connections within a proxy connection pool reaches zero, problems may occur.

Use the following CLI command, which uses the antivirus failopen feature. Setting it to idledrop will drop connections based on the clients that have the most connections open. This helps to determine the behavior of the FortiGate antivirus system if it becomes overloaded in high traffic.

Use the following CLI command, which gives you information about current memory usage: