Siemens SIMATIC HMI Series System Manual page 153

You system will only run on one server while you complete the phase 1 steps.
NOTICE
Procedure
In order not to interrupt operation of the system, observe the sequence of steps described.
Complete the steps in phases 1 to 4 without any longer interruption.
Note
Create a backup copy before upgrading the server.
Initial Situation Prior to Phase 1
● Server1 is the configured default master server.
(Server1 is synonym for any master server of a redundant pair of servers.)
● Server2 is the standby.
(Server2 is synonym for any standby server of a redundant pair of servers.)
● WinCC Client1 is connected to Server1.
The package of the master server is loaded onto WinCC Client1.
● (WinCC Client1 is synonym for all WinCC clients that were originally connected to Server1
and which have to be reconnected with Server1 after migration.) WinCC-Client2 is
connected to Server2 because this is its configured preferred server.
The master server package is loaded on WinCC Client2.
(WinCC-Client2 is synonym for all WinCC clients that were originally connected to Server2
and which have to be reconnected with Server2 after migration.)
Procedure, Phase 1
For a detailed description of the procedure, please click one of the following working steps.
Note
Please note that you must work alternately on Server1 and Server2.
1. WinCC Client1: Configure Server1 as preferred server
So that each client is connected with the associated server during the upgrade, a preferred
server must be configured for all clients in the system.
If a preferred server is not yet configured for WinCC Client1, then enter Server1 as the preferred
server.
Deactivate WinCC Client1 and reactivate the client so that the changed preferred server is
applied.
WinCC: General information and installation
System Manual, 02/2017, A5E40840020-AA
5.9 Upgrading a Redundant System in Normal Operation
Migration
153