Explanation
Unlike the App-ID engine, which inspects application packet contents for unique signature elements, the Application Override policy's matching conditions are limited to header-based data only. Traffic matched by an Application Override policy is identified by the App-ID entered in the Application entry box.Choices are limited to applications currently in the A Because this traffic bypasses all Layer 7 inspection, the resulting security is that of a Layer-4 firewall. Thus, this traffic should be trusted without the need for Content-ID inspection. The resulting application assignment can be used in other firewall functions such as Security policy and QoS.Use CasesThree primary uses cases for Application Override Policy are:
To identify "Unknown" App-IDs with a different or custom application signature To re-identify an existing application signature To bypass the Signature Match Engine (within the SP3 architecture) to improve processing timesA discussion of typical uses of application override and specific implementation examples is here:
https://live.paloaltonetworks.com/t5/Learning-Articles/Tips-amp-Tricks-How-to-Create-an-Application- O

Explanation/Reference:
Reference: https://www.paloaltonetworks.com/documentation/80/pan-os/web-interface-help/device/device- dynamic-updates