The Siemens part number 6AV6355-1AA31-7EF0 refers to the WinCC OA V3.17 Redundancy license. This software option enables high availability by allowing a redundant server setup with seamless switchover between servers in case of failure.

Here’s what you should know:

It’s a download-only license.

Required for each server in a redundant pair—both servers need this license.

Ensures smooth transition and system reliability in critical SCADA environments.

This is essential if you're building a fault-tolerant automation system where uptime is non-negotiable.