computer science

Rollback (data management)

Rollback (data management) is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Rollback (data management) rather than just read about it. In short: In database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed.

Key takeaways

Rollback (data management) belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Rollback (data management) to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Rollback (data management) from memory before moving on to harder problems.

Reference excerpt

In database technologies, a rollback is an operation which returns the database to some previous state. Rollbacks are important for database integrity, because they mean that the database can be restored to a clean copy even after erroneous operations are performed. They are crucial for recovering from database server crashes; by rolling back any transaction which was active at the time of the crash, the database is restored to a consistent state. The rollback feature is usually implemented with a transaction log, but can also be implemented via multiversion concurrency control.

Cascading rollback A cascading rollback occurs in database systems when a transaction (T1) causes a failure and a rollback must be performed. Other transactions dependent on T1's actions must also be rollbacked due to T1's failure, thus causing a cascading effect. That is, one transaction's failure causes many to fail. Practical database recovery techniques guarantee cascadeless rollback, therefore a cascading rollback is not a desirable result. Cascading rollback is scheduled by dba.

SQL SQL refers to Structured Query Language, a kind of language used to access, update and manipulate database. In SQL, ROLLBACK is a command that causes all data changes since the last START TRANSACTION or BEGIN to be discarded by the relational database management systems (RDBMS), so that the state of the data is "rolled back" to the way it was before those changes were made. A ROLLBACK statement will also release any existing savepoints that may be in use. In most SQL dialects, ROLLBACKs are connection specific. This means that if two connections are made to the same database, a ROLLBACK made in one connection will not affect any other connections. This is vital for proper concurrency.

Usage outside databases Rollbacks are not exclusive to databases: any stateful distributed system may use rollback operations to maintain consistency. Examples of distributed systems that can support rollbacks include message queues and workflow management systems. More generally, any operation that resets a system to its previous state before another operation or series of operations can be viewed as a rollback.

See also Savepoint Commit Undo Schema migration

Notes

References Ramez Elmasri (2007). Fundamentals of Database Systems. Pearson Addison Wesley. ISBN 978-0-321-36957-4. "ROLLBACK Transaction", Microsoft SQL Server. "Sql Commands", MySQL.

Worked examples

Example 1 — a first encounter with Rollback (data management)

Start with the simplest possible case. Write down what Rollback (data management) claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Rollback (data management) before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Rollback (data management) ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Rollback (data management)

In research: Rollback (data management) appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Rollback (data management) in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Rollback (data management) is common in secondary-school and first-year university syllabi. It links to neighbouring topics Database management systems, Database theory, Reversible computing, so understanding it makes those chapters shorter.
In everyday life: Look for Rollback (data management) outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Rollback (data management) in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Rollback (data management) means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Rollback (data management) out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Rollback (data management) in simple terms?

Why does Rollback (data management) matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Rollback (data management)?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Rollback (data management).