Siemens SIMATIC PCS 7 Function Manual page 225

Note
Encrypted communication
If you have used encrypted communication, it is activated in migration mode for all PC stations
in the system. Use encrypted communication in migration mode only as a temporary solution.
Deactivate migration mode in the entire system. You can find information about this in the
documentation
Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA
Failure, Switchover and Return of Fault-tolerant Components
6.10 Guidelines for updating a redundant OS in runtime
Process Control System PCS 7; PCS 7 PC Configuration .
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