Even if
the underlying server platform is fine, the Oracle instance itself can fail. Whatever
the cause of the crash, the effect on Oracle is the same??”the instance cannot deliver
Figure 11-2. Components of a system
Availability and
functionality
required at all
levels
Client
Middleware
Network Hardware
and Software
Application
Application Server Hardware
and Operating System
Database
Database Server Hardware and Software
Operating Sites and Facilities
THE SYSTEM STACK
258 | Chapter 11: Oracle and High Availability
its promised functionality. Remember that when an Oracle database crashes, it is the
instance that crashes, not the database (as described in Chapter 2). Even if the system
fails, the failure will not imperil any data that??™s already safely stored within the
disk files used by the Oracle database.
The impact of a crash will depend on the activity in progress at the time of the crash.
Any connected sessions will no longer have a server process to which to talk. All
active queries and transactions will be abruptly terminated.
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