Question

What is the purpose of transactions that have a [start_transaction,T] entry into the log but no [commit,T] entry into the log?

1) To rollback the transaction
2) To commit the transaction
3) To save the transaction for future use
4) To ignore the transaction

Answer 1

Transactions with [start_transaction, T] but no [commit, T] in the log are meant to be rolled back, suggesting an incomplete transaction that needs to be undone for data integrity.

Step-by-step explanation:

The purpose of transactions in a database log that have a [start_transaction, T] entry but no [commit, T] entry is typically to rollback the transaction. This scenario often indicates that the transaction has not been completed successfully. The absence of a commit entry suggests that the transaction may have been aborted, and as such, any changes it made to the database need to be undone to maintain data integrity. In database management systems, this process is crucial for handling situations where a transaction cannot be completed due to various reasons like system crashes, concurrency conflicts, or user-initiated aborts.