The message is somewhat cryptic but becomes clear if you
interpret it very literally. Oracle works using a pipe to communicate between the client
application and its associated server process in the Oracle instance. When the instance
fails, the client??™s server process ceases to exist, so there is no one listening on the other
end of the pipe. The communication channel between the client and the server is no
longer valid.
ORA-01034: Oracle not available
This terse message means that when the client requested a connection to the Oracle
instance, the instance was not there. Clients that try to connect to a failed instance will
typically get this message. The client can connect to the Listener, but when the Listener
attempts to hand the client off to the requested Oracle instance, the ORA-01034 condition
results.
System Failure | 259
of the transaction to the current online redo log and has sent back a message to the
client application confirming the committed transaction.
Phases of Instance Recovery
Instance recovery has two phases: rollforward and rollback.
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