4.6 Solutions for OS clients
4.6.1 Additional OS clients
Additional OS clients
OS clients are PC stations that are used for control and monitoring of an automation process.
They are connected to the OS servers through the terminal bus. The OS servers form the
process connection to the automation system.
An OS client has its own WinCC project and visualizes the process data generated on an OS
server.
If an OS client fails, this does not disrupt the overall process because the automation program
in the CPU continues to control the process and the OS servers continue to process and archive
the process data. However, the visualization of the process is lost and you can only influence
the process through the OS servers. You should therefore protect against such failure by
integrating additional OS clients.
By specifying a preferred server, you can distribute multiple OS clients between the redundant
OS servers. The automation process can therefore be operated continuously, even during a
switchover from the active OS to its OS partner server.
Additional information
● Section " How to configure an OS client (Page 163) "
● Online help for
WinCC
4.6.2 Permanent operability
Permanent operability
"Permanent operability" in a redundant environment is the unrestricted ability to influence the
system at any time even when confronted with the failure of one of the redundant OS servers.
It is the most important safety characteristic for plants with critical operations.
This function is important in all systems in which the ability to handle failure of an OS server
in a redundant configuration is not enough and in which continuous control of a process must
be maintained. In the event of an OS server failure, all OS clients connected to the failed server
temporarily lose their connection to the process while they switch over. In order to ensure that
the OS clients can control and monitor the automation process continuously, the OS clients
are distributed between the redundant OS servers with specification of a preferred OS server.
The failure of some OS clients can therefore be tolerated because the other clients remain
connected to the process.
High availability solutions in PCS 7
4.6 Solutions for OS clients
High Availability Process Control Systems (V9.0)
Function Manual, 05/2017, A5E39221836-AA 97
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