RE: DataGuard

>From: Boris Dali [mailto:boris_dali_at_yahoo.ca]
>'Split-brain' scenario of having more than one database accepting
connections in a broker configuration is prevented by the rule that two out of three participants in the broker config should agree before failover is attempted. There's a brand-new paper on the MAA site about it:
http://www.oracle.com/technology/deploy/availability/pdf/MAA_WP_10gR2_Fa stStartFailoverBestPractices.pdf

I was asking about a different scenario:

Assume Observer misses network connection to the Primary for whatever reason. Will it assume the Primary dead? It should I believe. This is the whole purpose of it.
What then prevents client A to connect to the Standby (which is opened as the Second Primary now) and client B to the Primary(the First Primary)? Note that client B can either find a way to get network connection to the First Primary or the connection may simply become available again after some time. I can easily imagine both cases may happen in today's complex network environments.

As I see it the only credible solution is either a) to have a single point (of failure) for all incoming client connections or b) to reconfigure all Oracle clients (change of tnsnames.ora for example)

Next issue: Oracle paper above suggests "Maximum Availability" DG configuration. Yet it states that:
"For example, if the production database becomes unavailable, the Observer confirms with the target standby database that the production database is unavailable and that the target standby database is synchronized with the production database, and if so, initiates a fast-start failover to the target standby database."

The question is: how Observer is able to detect that standby is actually synchronized with the primary?
What standby needs to know is that primary was not operating in the downgraded Maximum Performance mode before its death. Is this information available on the standby DB?

Fyrirvari/Disclaimer
http://www.landsbanki.is/disclaimer

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