Os Server; Failure, Failover And Restarting Of Redundant Os Servers - Siemens SIMATIC PCS 7 Function Manual

Failure, Switchover and Return of Fault-tolerant Components

6.4 OS server

6.4 OS server
6.4.1

Failure, failover and restarting of redundant OS servers

Introduction
This section describes the criteria by which the master/standby identification of an OS server
changes. Examples are given to illustrate how the system reacts to failures.
Note
Information on updating operator stations with redundant OS servers in runtime can be found
in "guidelines on updating a redundant OS in runtime (Page 208)".
Fault scenarios
● The project is not activated on the redundant OS partner server.
● The network connection from the OS server to the redundant OS partner is disrupted.
● The network connection to the OS clients is disrupted.
● The process connection to the AS is disrupted.
● The PC station is not operating correctly.
Reaction of WinCC redundancy to possible faults
WinCC redundancy can react to faults, errors or error messages in the following ways:
● By saving events and the time they occurred
● By synchronizing the archives of the process data (Tag Logging) and message data (Alarm
Logging) with the archive data of the active OS server when a failed OS server is recovered.
● By changing the system tags "@RM_MASTER" and "@RM_MASTER_NAME" according
to the situation.
● By automatically interconnecting the OS clients with the preferred server or with the
available OS server with master identification. The "@RM_SERVER_NAME" tag indicates
for an OS client the OS server to which this OS client is currently connected.
● By generating process control messages in the message list.
The fault scenarios listed above and the resulting reactions by WinCC Redundancy are
described in the following.
196
Fault-tolerant Process Control Systems (V8.1)
Function Manual, 11/2014, A5E34878832-AA