Siemens SIMATIC PCS 7 Configuration Manual page 218

Configuring OS functions
10.1 Project settings
Computer properties in the OS client project
You must also make the following settings in the properties dialog of the computer:
Settings in the "Time Synchronization" editor in the OS server projects
The OS clients receive their time from an OS server on the terminal bus.
You need to make the following settings in the OS projects of the clients, in the "Time
Synchronization" editor:
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Compendium Part A - Configuration Guidelines (V8.2)
Configuration Manual, 08/2016, A5E38166869-AA