Synchronization of Triple Redundant or Triple Redundant with Permanent Standby Systems

[Hardin4019]

I can't find anywhere in the help files that specifically says it (at least in the way I am saying), but what I suspect, and believe I have observed first hand to be true is that a Standby or Permanent Standby server will only synchronize to the server that is currently Main and listed as a Partner in the Server Configuration. Is that accurate?

I'm working with a Triple Redundant with Permanent Standby system. When the Primary server fails, the Permanent Standby server goes offline waiting to connect. The Permanent Standby's Partners don't include the first Standby server that becomes main if the Primary server fails. The Permanent Standby server remains offline until the Primary server becomes main again.

[BevanWeiss]

Is this looking at the server status itself, or how it appears to ViewX clients?

There is this tick box in the Client Configuration dialog which will prevent connections to 'un-synchronised' servers from ViewX (or other clients using these settings).  This would include any 'standby' servers which are not actively connected to the Main server.

If you consider any ClearSCADA architecture, and remove the Main/Duty server, then you don't really have a valid ClearSCADA system.  Since 'Standby' really just means, 'Slave' to the Main (Duty/Active Database)... without a Main there is no valid ClearSCADA system, so nothing for the Standbys to be a slave to.  Them going Offline [or at least exiting the Standby state] (after the expiry of their heartbeat times etc) does make sense.  They should however resume their role as Standby after a Main is brought back up and they have synchronised to it.

Having them still serve 'data' (Config/Data/Historic Data/etc) which may actually not be at all related to the Main Database would typically not be the appropriate thing to do (after all, only the Main server is allowed to create records such as 'Last Known Value' / alarms etc)

[adamwoodland · Accepted solution]

Yes, a server can only sync to a Main and as long as it is configured to see it

[JChamberlain]

There is a tool on Resource Center that may help, link.

[Hardin4019]

Thanks for confirming and sharing the links guys.

[sbeadle]

1) a Main server can send database sync data to 5 other servers max, 2 standby max and 4 standby-only max. (e.g. total 2 Main/Standby and 4 Standby-only or 3 Main/Standby and 3 Standby-Only)

2) BUT a Standby server can be synced from a max of two servers.

This means that a standby-only can be synced from only two of a triple server set, which is why that link in the post above is needed, which is a tool to "switch parents" of a Standby-Only.