Notes On Wincc Redundancy - Siemens SIMATIC HMI Series System Manual

2.4

Notes on WinCC Redundancy

Redundancy behavior in case of double failure
Double failures are not covered by redundancy.
A double failure occurs, for example, when the terminal bus was pulled on server 1 while server
2 was deactivated.
Delay in swapping out archives
The swapping of archives will be delayed if a redundant partner is not available or deactivated..
Swapping of archives will not start or continue until the partner is available once again and
after archive synchronization.
An extended failure of the redundant partner may result in data loss, because the memory
capacity of the circular buffer for Tag Logging and Alarm Logging is limited.
No reloading of messages after network failure
The reloading of messages after network failure is not permitted for redundant systems.
Configuring used standard gateway
For redundancy, it is recommended to configure a standard gateway for the correct detection
of failure scenarios. The standard gateway must be properly configured on both redundancy
servers for this. This can be done manually or via DHCP.
For a configured standard gateway, ensure that this gateway cannot only be reached but is
also accessible using a "ping".
Use of DHCP: Starting computer only with active network connection
If you are using DHCP on the terminal bus network card, note the following in a redundant
system:
The computer must obtain a valid IP address from the DHCP server during startup.
Otherwise, the redundancy status is always indicated as "fault". This status can only be reset
by restarting the computer.
Message sequence report in a redundant system
If you output a message sequence report on a client, you may encounter problems during
logging when switching to the redundant partner.
WinCC: General information and installation
System Manual, 02/2017, A5E40840020-AA
WinCC Release Notes
2.4 Notes on WinCC Redundancy
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