High
availability and reliability are becoming more important in the
automation technology. Even a short breakdown can result in heavy
costs and security risks. The redundancy is used to guarantee
plant management without any adverse effects in case of a failure
and thus loss of data and associated problems do not occur.
The
reliability in a redundant system with WinCC OA
is implemented via hot standby. Hot standby is a hardware independent
solution for high availability. This is a security concept consisting
of two server systems connected with each other. Both servers
are operating permanently and are subject to same functional demands
(only one server is, however, always active. The second server
synchronizes the data at runtime with the primary unit). If a
unit fails a "flying switch" is executed and the server,
which was passive until then, takes over the control. Thus, the
access to data or functions is always guaranteed. |