Transaction States

Transaction States                       

AU: May-14,18, Dec.-11,19, Marks 8

Each transaction has following five states:

1) Active: This is the first state of transaction. For example: insertion, deletion or updation of record is done here. But data is not saved to database.

2) Partially Committed: When a transaction executes its final operation, it is said to be in a partially committed state.

3) Failed: A transaction is said to be in a failed state if any of the checks made by the database recovery system fails. A failed transaction can no longer proceed further.

4) Aborted: If a transaction is failed to execute, then the database recovery system will make sure that the database is in its previous consistent state. If not, it brings the database to consistent state by aborting or rolling back the transaction.

5) Committed: If a transaction executes all its operations successfully, it is said to be committed. This is the last step of a transaction, if it executes without fail.

Example 3.3.1 Define a transaction. Then discuss the following with relevant examples:

1. A read only transaction 2. A read write transaction 3. An aborted transaction

Solution:

(1) Read only transaction

(2) A read write transaction

(3)

Review Questions

1. During execution, a transaction passes through several states, until it finally commits or aborts. List all possible sequences of states through which transaction may pass. Explain why each state transaction may occur?AU: May-18, Marks 6

2. With a neat sketch explain the states of transaction.AU: May-14, Marks 8

3. Brief the states of a transaction with a neat diagram.AU: Dec 19, Marks 4