Tuesday, 11 February 2014

STATES OF TRANSACTION

A transaction must be in one of the following states.
1.Active-The initial state,the transaction stays in this state while it is executing.
2.Partially committed- After the final statement has been executed.
3.Failed-when the normal execution can no longer proceed.

4.Aborted-After the transaction has been rolled back and the database has been restored to its state prior to the start of the transaction.
5.Committed-After successful completion.


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 residing in main memory and thus a hardware failure may preclude its successful completion.

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