Discuss the timestamp ordering protocol for concurrency control. How does strict timestamp ordering differ from basic timestamp ordering?

Timestamp Ordering Protocol is a concurrency control protocol that is used in the database transactions to schedule operations in such a way that the chronological order is maintained based on their timestamps. The main goal of this protocol is to avoid conflicts that could lead to concurrency related problems like dirty reads, non-repeatable reads, and phantom reads.

Here's how it works:

1. Each transaction is assigned a unique timestamp when it enters the system.
2. If a transaction wants to read an object, it is allowed to do so only if its timestamp is greater than the timestamp of the last transaction that wrote to the object.
3. If a transaction wants to write an object, it is allowed to do so only if its timestamp is greater than the timestamps of all transactions that have read or written the object.

Strict Timestamp Ordering is a variant of the basic Timestamp Ordering protocol. The main difference between the two lies in the handling of write operations:

1. In basic Timestamp Ordering, a transaction can write an object if its timestamp is greater than the timestamps of all transactions that have read or written the object. This means that a transaction can write an object even if there are other transactions that have read the object but not yet committed.
2. In Strict Timestamp Ordering, a transaction can write an object only if its timestamp is greater than the timestamps of all transactions that have read or written the object and all those transactions have committed.

The advantage of Strict Timestamp Ordering is that it prevents cascading rollbacks, which can occur in basic Timestamp Ordering. A cascading rollback happens when a transaction needs to be rolled back, causing other transactions that have read data from it to also be rolled back. This can lead to a cascade effect where many transactions need to be rolled back, which can be very costly in terms of system performance.