RE: DataGuard
- From: "Laimutis Nedzinskas" <Laimutis.Nedzinskas@xxxxxxxxxxxxx>
- To: <oracle-l@xxxxxxxxxxxxx>
- Date: Fri, 19 Jan 2007 10:23:25 -0000
>From: Boris Dali [mailto:boris_dali@xxxxxxxx]
>'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
--
//www.freelists.org/webpage/oracle-l
Other related posts:
