Chapter 18: Problem 10

What is a certify lock? What are the advantages and disadvantages of using certify locks?

Short Answer

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A certify lock is a concurrency control method used in databases to protect data during a transaction. It prevents conflicts by ensuring that other transactions cannot modify the data until the original transaction is completed. Advantages include enhanced system performance, enabling of multiple read operations simultaneously, and prevention of Phantom Read phenomena. However, disadvantages include potential resource holding, vulnerability to deadlocks, high abort rates in high contention scenarios, and imposing high certification cost.

Step by step solution

Understand what a Certify Lock is

A certify lock, also known as a certification lock, is a concurrency control method used in databases. It is part of an operation that protects data during a transaction, and prevents conflicts by ensuring that other transactions cannot modify the data until the process is completely finished. The lock remains until the transaction completes, either successfully with a commit or unsuccessfully with a rollback.

Identify the advantages of Certify Locks

There are several advantages of using certify locks. Firstly, certify locks can enhance system performance by reducing the time that locks held. They are used by transactions only at commit time, reducing waiting time. Secondly, they allow multiple read operations to occur simultaneously which is beneficial in a multi-user environment. Lastly, certify locks can prevent the Phantom Read phenomenon which occurs when a transaction re-executes a query and finds new rows that were not there in the previous execution of the same query.

Discuss the disadvantages of Certify Locks

Whilst certify locks have a lot of advantages, there are also some disadvantages. The main issue is that transactions may hold up resources for a long time without being aware of it, thus causing vulnerability to deadlocks. Also, certify locks can lead to high abort rates in scenarios of high contention as they work by failing any conflicting transactions. Lastly, it might impose a high certification cost, as we need to lock and release all data items at end of transaction, this can be very costly for large transactions.

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What is a certify lock? What are the advantages and disadvantages of using certify locks?

Short Answer

Step by step solution

Understand what a Certify Lock is

Identify the advantages of Certify Locks

Discuss the disadvantages of Certify Locks

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