Siemens Simatic PCS 7 Function Manual page 95

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.
High Availability Process Control Systems (V9.0)
Function Manual, 05/2017, A5E39221836-AA
High availability solutions in PCS 7
4.5 Solutions for OS servers
95