You are in the middle of a transaction and very crucial data has been modified. Because of a hardware failure, the instance has shut down before synchronizing all the database files.
Which two statements are true? (Choose two.)
A. On startup, SMON coordinates instance recovery.
B. On startup, CKPT coordinates instance recovery.
C. On startup, use RMAN to perform instance recovery.
D. Uncommitted changes will be rolled back after the database is opened.
E. On startup, perform media recovery and then instance recovery.
F. On startup, all the files will be synchronized and you get both committed and uncommitted data.
Answer: AD
When Oracle Database Performs Instance Recovery
Whether instance recovery is required depends on the state of the redo threads. A redo thread is marked open in the control file when a database instance opens in read/write mode, and is marked closed when the instance is shut down consistently. If redo threads are marked open in the control file, but no live instances hold the thread enqueues corresponding to these threads, then the database requires instance recovery.
Oracle Database performs instance recovery automatically in the following situations:
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The database opens for the first time after the failure of a single-instance database or all instances of an Oracle RAC database. This form of instance recovery is also called crash recovery. Oracle Database recovers the online redo threads of the terminated instances together.
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Some but not all instances of an Oracle RAC database fail. Instance recovery is performed automatically by a surviving instance in the configuration.
The SMON background process performs instance recovery, applying online redo automatically. No user intervention is required.
When a ROLLBACK statement is issued, undo records are used to undo changes that were made to the database by the uncommitted transaction. During database recovery, undo records are used to undo any uncommitted changes applied from the redo log to the data files. Undo records provide read consistency by maintaining the before image of the data for users who are accessing the data at the same time that another user is changing it.