Database Transaction States to Know for Intro to Database Systems

Understanding database transaction states is crucial for maintaining data integrity and consistency. These states—active, partially committed, committed, failed, aborted, and terminated—describe the lifecycle of transactions and how they interact within a database system.

1. Active

   • The transaction is currently being executed and is in progress.
   • It can read and write data to the database.
   • The transaction remains in this state until it reaches a decision point (commit or abort).
   • Multiple transactions can be active simultaneously in a database system.

2. Partially Committed

   • The transaction has executed its final operation but has not yet been committed.
   • Changes made during this state are not yet permanent and can still be rolled back.
   • This state indicates that the transaction is in the process of finalizing its changes.
   • It is a transitional state that occurs after the last operation but before the commit.

3. Committed

   • The transaction has successfully completed all operations and is now permanent in the database.
   • Changes made during the transaction are now visible to other transactions.
   • This state ensures data integrity and consistency in the database.
   • Once committed, the transaction cannot be undone.

4. Failed

   • The transaction has encountered an error that prevents it from completing successfully.
   • It may result from issues like system crashes, deadlocks, or constraint violations.
   • In this state, the transaction must be rolled back to maintain database integrity.
   • The system may log the failure for recovery and troubleshooting purposes.

5. Aborted

   • The transaction has been intentionally terminated before it could be committed.
   • This can occur due to user intervention or system decisions based on error detection.
   • All changes made during the transaction are discarded, restoring the database to its previous state.
   • Aborted transactions help maintain consistency and prevent partial updates.

6. Terminated

   • The transaction has completed its lifecycle, either through successful commit or abort.
   • In this state, all resources held by the transaction are released.
   • The system can now reclaim memory and other resources associated with the transaction.
   • Termination signifies that the transaction is no longer active and has no further impact on the database.