Timestamp-based protocols in DBMS Theory - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the main purpose of timestamp-based protocols in databases?

Timestamp-based protocols help manage the order of transactions to avoid conflicts and ensure consistency by using timestamps to decide which transaction should proceed.

beginner

How does a timestamp determine the order of transactions?

Each transaction is given a unique timestamp when it starts. Transactions with smaller timestamps are considered older and get priority over newer ones.

intermediate

What happens if a transaction tries to access data that conflicts with a newer transaction in timestamp-based protocols?

The older transaction may be rolled back or delayed to maintain the correct order, preventing conflicts and ensuring data consistency.

intermediate

Explain the difference between read and write timestamps in timestamp-based protocols.

Read timestamp records the last time data was read, and write timestamp records the last time data was written. These help decide if a transaction can safely read or write data without conflicts.

advanced

Why are timestamp-based protocols considered non-locking concurrency control methods?

Because they do not use locks to control access but rely on timestamps to order transactions, reducing waiting times and deadlocks.

What does a smaller timestamp indicate in timestamp-based protocols?

A An older transaction

B A newer transaction

C A transaction with higher priority to write

D A transaction that must be rolled back

Smaller timestamps mean the transaction started earlier, so it is older and usually given priority.

In timestamp-based protocols, what happens if a transaction tries to write data that has been read by a newer transaction?

A The newer transaction is rolled back

B The write is allowed immediately

C The transaction is rolled back

D Both transactions proceed simultaneously

To maintain order, the older transaction must roll back if it tries to write data already read by a newer transaction.

Which of the following is NOT a feature of timestamp-based protocols?

A Assigning unique timestamps to transactions

B Use of locks to control access

C Ordering transactions by timestamp

D Avoiding deadlocks

Timestamp-based protocols do not use locks; they rely on timestamps to order transactions.

What do read and write timestamps help determine?

A If a transaction can safely read or write data

B The size of the transaction

C When to commit a transaction

D The priority of the database server

Read and write timestamps help decide if a transaction can access data without causing conflicts.

Why might a transaction be rolled back in timestamp-based protocols?

A Because it has the newest timestamp

B Because it completed successfully

C Because it requested a lock

D Because it conflicts with the order of timestamps

Transactions that violate the timestamp order are rolled back to maintain consistency.

Describe how timestamp-based protocols use timestamps to manage transaction order and avoid conflicts.

Think about how the system decides which transaction goes first.

Explain the role of read and write timestamps in timestamp-based concurrency control.

Consider how the system knows if data access is safe.