Transaction Processing Concepts, Concurrency and Recovery What is the difference

Question

Transaction Processing Concepts, Concurrency and Recovery

What is the difference between the partially-committed state and the committed state? A. In partially-committed state, system failure will result in aborted transaction. In committed state, transaction concludes execution successfully. All changes are recorded permanently in database. B. Partially-committed state is when a database is doing more than one read write from different locations and committed state is from one location C. In a fully commited state all data is saved to the database and querying data will not result in errors. A partially committed transaction will produce invalid results. D. Partially-committed state data and ops are stored in a log in case disaster recovery is needed. Committed state data is stored to the disk. E. Committed state is stable because all changes by transactions are written permanently. Partially-committed state is unstable because changes by transactions can be rolled back.

Explanation / Answer

Please go through the data for the explanation :

We say that a transaction has committed only if it has entered the committed state. Similarly, we say that a transaction has aborted only if it has entered the aborted state. A transaction is said to have terminated if has either committed or aborted.

A transaction starts in the active state. When it finishes its final statement, it enters the partially committed state. At this point, the transaction has completed its execution, but it is still possible that it may have to be aborted, since the actual output may still be temporarily hiding in main memory and thus a hardware failure may preclude its successful completion

The database system then writes out enough information to disk that, even in the event of a failure, the updates performed by the transaction can be recreated when the system restarts after the failure. When the last of this information is written out, the transaction enters the committed state.

Partially Committed:

At any given point of time if the transaction is executing properly, then it is going towards it COMMIT POINT. The values generated during the execution are all stored in volatile storage.

or

A database transaction enters this phase when its final statement has been executed. At this phase, the database transaction has finished its execution, but it is still possible for the transaction to be aborted because the output from the execution may remain residing temporarily in main memory - an event like hardware failure may erase the output.

Committed:

If no failure occurs then the transaction reaches the COMMIT POINT. All the temporary values are written to the stable storage and the transaction is said to have been committed.

or

A database transaction enters the committed state when enough information has been written to disk after completing its execution with success. In this state, so much information has been written to disk that the effects produced by the transaction cannot be undone via aborting; even when a system failure occurs, the changes made by the committed transaction can be re-created when the system restarts.

Log or Journal:

The log keeps track of all transaction operations that affect the values of database items.
This information may be needed to permit recovery from transaction failures.
The log is kept on disk, so it is not affected by any type of failure except for disk or catastrophic failure.
In addition, the log is periodically backed up to archival storage (tape) to guard against such catastrophic failures.

So from the above data it can be observed clearly that the OPTION A suits the differences.

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