OS partner servers (OS_Stby) are configured in the SIMATIC Manager. Using the menu 
command PLC > Download synchronizes the functionality.
Redundant external archive server 
You use the Process Historian for central acquisition of archive information of the process 
control system. You can set up two Process Historians with redundancy functionality for high 
availability operation. The associated information server can be configured in such a way that 
it connects to the active Process Historian to execute tasks.
If a Process Historian of a server pair fails, the data is automatically synchronized on the return 
of the failed server.
This server does not require a connection to the plant bus.
Redundant maintenance station
PCS 7 allows you to configure two maintenance servers with redundancy functionality for high 
availability operation.
Setting up a redundant OS server
The following configuration shows the basic operating principle of redundant OS servers.
Note
You need to connect the redundant PC stations through a redundancy connection. This 
connection offers security against problematic behavior during communication between the 
OS servers.
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High availability solutions in PCS 7
4.5 Solutions for OS servers
High Availability Process Control Systems (V9.0)
Function Manual, 05/2017, A5E39221836-AA 95