Redundancy - Both servers active

[vsolomonidou]

Hi,

In a redundant system if the redundancy partners lose the connection to each other, both WinCC OA projects become active.

Do you know how long it takes before the standby switches to active?

Thanks,

Vaso

[amichon]

Hi Vaso,

When the network connection is lost between the two partners, both partners become active. It is quite normal that they do not go into passive mode.

To avoid this behavior, you can use redundant network connections between the servers.

I hope this will be useful to you.

BR

Aurélien

[vsolomonidou]

Thanks Aurélien.

I was wondering how long it takes for both partners to become active? Is it immediately as soon as the servers detect the broken link, or after X number of seconds (where X can be configured)?

Thanks,
Vaso

[leoknipp]

There are 2 possibilities that a WinCC OA process detects that a connection is lost:
-- Getting the information from theTCP stack (operating system)
-- Reaching the alive timeout for the connection (configured with aliveTimeout config entry, default 10 seconds)

For the connection between WinCC OA processes you must not use an aliveTimeout lower than 3 seconds.

Best Regards
Leopold Knipp
Senior Support Specialist

[vsolomonidou]

Thanks Leopold, that's really helpful.

On a similar note, we also have redundant video servers. Are you able to tell me how long the connection between the duty SCADA server and the and active video server has to be down before the duty SCADA server (video manager) instructs the redundant video server to take over?

Thanks,
Vaso

[leoknipp]

For the Video server I do not know how redundancy and the connection check works in detail as it is a 3rd party software.
If you want to have you can possibly ask the software vendor for the video software or get in contact with your common WinCC OA support.

Best Regards
Leopold Knipp
Senior Support Specialist