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In my experiences, the terms "active-active" and "active-passive" mean
different things to different people. So, let's not bother labeling the two
main configurations (at least that's what I think you're talking about) and
just explain them.
With multi-instance databases in Oracle, you can optionally set the
active_instance_count parameter. If set to 1, then one instance will assume
the "primary" role and it will allow sessions to connect directly to it. All
other instances will have the "secondary" role until the primary instance
fails. When the primary instance fails, one of the secondary instances will
assume the primary role and begin accepting connections. There are a number
of reasons that this configuration is useful, and it is typically used to
provide very fast failover. This is useful for applications that require
faster failover than a traditional failover cluster but that cannot run in a
parallel configuration due to an application design problem (all users update
one row in one table or any number of other related issues).
When the active_instance_count is set to a value other than 1 (or it is not
set at all), then users may connect to any instance. This is what most people
think of as a "true" parallel database since processing is taking place on
multiple nodes at the same time. In versions prior to 9i, this was the
configuration that required very careful planning and design to avoid
pings created when application users touch the same data from multiple
instances.
In general, most people refer to an "active-passive" configuration as the
first one I've described (when active_instance_count is set to 1) and
"active-active" is commonly associated with the second case where users are
active on more than one node simultaneously.
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