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Oracle

1Z0-052 · Question #67

You are in the middle of a transaction updating a very important table. The machine on which a database was running reboots because of power outage. This caused a database instance failure. Which…

The correct answer is C. The uncommitted transaction is rolled back automatically at the next opening of the database. Oracle performs automatic instance recovery at the next startup after a crash, rolling forward committed changes and automatically rolling back any uncommitted transactions - no DBA intervention is required.

Managing the Database Instance

Question

You are in the middle of a transaction updating a very important table. The machine on which a database was running reboots because of power outage. This caused a database instance failure. Which statement is true in this situation?

Options

  • AThe online redo log files and archived redo log files are required to accomplish the recovery
  • BThe uncommitted transaction will be committed at the next startup of the database instance
  • CThe uncommitted transaction is rolled back automatically at the next opening of the database
  • DThe DBA has to perform the recovery on the database to recover the uncommitted transaction

How the community answered

(50 responses)
  • A
    4% (2)
  • B
    2% (1)
  • C
    88% (44)
  • D
    6% (3)

Why each option

Oracle performs automatic instance recovery at the next startup after a crash, rolling forward committed changes and automatically rolling back any uncommitted transactions - no DBA intervention is required.

AThe online redo log files and archived redo log files are required to accomplish the recovery

Archived redo log files are not needed for instance recovery because the crash occurred mid-transaction and the required redo is contained entirely within the online redo logs that were active at the time of failure.

BThe uncommitted transaction will be committed at the next startup of the database instance

Oracle never commits uncommitted transactions on behalf of the user during recovery; committing an uncommitted transaction would violate ACID atomicity and could corrupt application data.

CThe uncommitted transaction is rolled back automatically at the next opening of the databaseCorrect

When an Oracle instance fails, the SMON background process performs automatic instance recovery during the next database open using the online redo log files. It first rolls forward all changes recorded in the redo logs (including uncommitted ones) to restore the data files to a consistent post-crash state, then automatically rolls back any transactions that were uncommitted at the time of failure using undo segments. This entire process is transparent and requires no DBA action.

DThe DBA has to perform the recovery on the database to recover the uncommitted transaction

Instance recovery from a crash is fully automatic via SMON and does not require any DBA intervention or manual recovery commands.

Concept tested: Automatic instance recovery and undo of uncommitted transactions

Source: https://docs.oracle.com/en/database/oracle/oracle-database/19/cncpt/oracle-database-instance.html#GUID-44CE9843-4228-4346-9DB9-B5B9A2B04B91

Topics

#instance recovery#crash recovery#uncommitted transactions#SMON

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