In some cases users may
experience a slight delay in response times, but their sessions aren??™t terminated. Clients
connected to the failed instance can reconnect to a surviving instance and can
resume working. Uncommitted transactions will be rolled back and will have to be
resubmitted. Queries that were active will also have been terminated; however,
Transparent Application Failover (TAF) can be used to automatically continue query
processing on a surviving node without requiring users to resubmit their queries.
You can also use TAF to resubmit transactions without user intervention.
Parallel Fail Safe/RACGuard
Oracle Parallel Fail Safe was renamed RACGuard in Oracle9i and integrated into the
core RAC product in Oracle Database 10g. Prior to Oracle Database 10g, it was a
feature in Real Application Clusters that leveraged the clustering software from systems
vendors. As of Oracle Database 10g, the database includes a cluster filesystem.
RACGuard supported such features as:
??? Automated, fast, and bounded recovery times from Oracle instance crashes
??? Automatic capture of diagnostic data
??? Guaranteed primary and secondary configuration
??? Support for features such as Transparent Application Failover (described in the
next section)
??? Client preconnection to secondary instances to speed reconnection
Oracle Transparent Application Failover
Oracle introduced the Transparent Application Failover (TAF) capability in the first
release of Oracle8.
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