Redundancy - Both servers active

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vsolomonidou
Posts: 20
Joined: Mon Mar 02, 2015 10:33 am

Redundancy - Both servers active

Post by vsolomonidou » Wed Nov 18, 2020 4:38 pm

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
Posts: 45
Joined: Sat May 17, 2014 1:49 pm

Re: Redundancy - Both servers active

Post by amichon » Wed Nov 18, 2020 6:59 pm

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
Posts: 20
Joined: Mon Mar 02, 2015 10:33 am

Re: Redundancy - Both servers active

Post by vsolomonidou » Thu Nov 19, 2020 9:17 am

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

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leoknipp
Posts: 2344
Joined: Tue Aug 24, 2010 5:28 pm

Re: Redundancy - Both servers active

Post by leoknipp » Thu Nov 19, 2020 9:51 am

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

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