Note that unlike query resubmission,
TAF itself doesn??™t automatically resubmit the transactions that were in-flight.
Rather, it provides a framework for a seamless failover that can be leveraged by
application developers.
Figure 11-7. Failover with TAF and Real Application Clusters
??? Client automatically reconnects to surviving instance
??? TAF can resubmit queries automatically
??? Applications can be made failover-aware and can resubmit transactions
Before Failure After Failure
Oracle
Instance
Oracle
Instance
Oracle
Instance
Oracle Database Oracle Database
274 | Chapter 11: Oracle and High Availability
How TAF works
TAF is implemented in the Oracle Call Interface (OCI) layer, a low-level API for
establishing and managing Oracle database connections. When the instance to
which a client is connected fails, the client??™s server process ceases to exist. The OCI
layer in the client can detect the absence of a server process on the other end of the
channel and automatically establish a new connection to another instance.
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