Redundancy Arbitration including ICMP Polls

[Anonymous user]

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The ICMP polls are used to ping the availability of the partner server. How the results of this ping is used depends on the "Action on Isolated" field on the "Partners" panel of the server configuration dialogue.

If "Action on Isolated" is set to "Go Main", the ICMP polls are ignored and the server goes main when the standby connection to the main is lost.

If "Action on Isolated" is set to "Go Isolated Standby", then both the standby connection and the ICMP polls are used to determine what the server does:

• If both the ICMP poll and the standby connection fails, the standby server is considered to be isolated from the main server. The standby server goes into an isolated standby state and waits for the main to re-appear. The user can manually switch the server into the main state if required.

• If the ICMP polls are ok, but the standby connection fails, then the server PC is considered to be accessible via the network, but ClearSCADA is no longer running on that server. In this case the standby server goes main.

• If the ICMP poll fails and the standby connection does not fail, the server continues in a standby state (an unlikely occurrence).

Setting "Action on Isolated" to "Go Isolated Standby" is recommended for main standby servers connected via a WAN link, where disruption to the link is a possibility. This settings avoids getting a main-main situation when the WAN link is temporarily unavailable.

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