Recoverability and Irrecoverability of Schedules in Database Management

Define fail-stop assumption.

In the system crash, non-volatile storage is assumed not to be corrupted.

What causes disk failure?

Disk failure occurs due to the formation of bad sectors, disk head crash, and unreachability to the disk.

Explain log-based recovery in databases.

Log-based recovery involves maintaining a sequence of transaction records in stable storage to recover from failures.

What is deferred database modification?

Deferred modification technique delays updating the database until a transaction has committed. Signup and view all the answers

How does a recoverable schedule differ from an irrevocable schedule?

A recoverable schedule can be undone if needed, while an irrevocable schedule cannot be rolled back. Signup and view all the answers

Explain the concept of a serial schedule in database transactions.

A serial schedule is where one transaction is executed completely before starting another transaction. Signup and view all the answers

What is the difference between a serial schedule and a non-serial schedule?

A serial schedule executes transactions one after the other with no interleaving, while a non-serial schedule allows interleaving of operations. Signup and view all the answers

How does the database recovery module handle transactions after aborting a transaction?

After aborting a transaction, the database recovery module can either re-start the transaction or kill the transaction. Signup and view all the answers

Define a schedule in the context of database transactions.

A schedule is a series of operations from one transaction to another, used to preserve the order of operations within each transaction. Signup and view all the answers

What is the purpose of serializability of schedules in database transactions?

Serializability helps in finding non-serial schedules that allow transactions to execute concurrently without interfering with each other. Signup and view all the answers

Describe the key characteristics of a serializable schedule.

A serializable schedule ensures that even if transactions execute concurrently, the end result is equivalent to some serial execution of those transactions. Signup and view all the answers

Explain the concept of serializability in transaction schedules.

Serializability in transaction schedules ensures that the result of a non-serial schedule is equal to the result of its transactions executed serially. Signup and view all the answers

What is a precedence graph used for in testing serializability?

A precedence graph is used to test the serializability of a schedule by representing the order of operations between transactions. Signup and view all the answers

How is a conflict serializable schedule defined?

A schedule is conflict serializable if it can be transformed into a serial schedule by swapping nonconflicting operations. Signup and view all the answers

What are the conditions for two operations to be considered conflicting in a schedule?

Two operations are conflicting if they belong to separate transactions and involve the same data item. Signup and view all the answers

Why is testing serializability important in database transactions?

Testing serializability ensures that concurrent transactions maintain consistency and do not lead to data corruption. Signup and view all the answers

Explain the significance of the precedence graph in identifying dependencies between transactions.

The precedence graph helps visualize the order of operations and potential conflicts between transactions in a schedule. Signup and view all the answers

Explain the concept of conflict equivalent schedules in the context of transaction schedules.

Two schedules are said to be conflict equivalent if they contain the same set of transactions and if each pair of conflict operations are ordered in the same way. Signup and view all the answers

What is the significance of a serial schedule in the context of transaction scheduling?

A serial schedule ensures that all operations of one transaction are performed before starting any operation of another transaction. Signup and view all the answers

How can a schedule be transformed into a serial schedule by swapping non-conflicting operations?

A schedule can be transformed into a serial schedule by ensuring that all operations of one transaction are performed before any operation of another transaction. Signup and view all the answers

Define conflict serializability in the context of transaction schedules.

Conflict serializability refers to the property of a schedule that can be transformed into a serial schedule by swapping non-conflicting operations. Signup and view all the answers

How does swapping non-conflicting operations contribute to conflict equivalent schedules?

Swapping non-conflicting operations allows schedules to be transformed into conflict equivalent schedules without affecting the final result. Signup and view all the answers

Explain the conditions under which two schedules are considered conflict equivalent.

Two schedules are considered conflict equivalent if they contain the same set of transactions and if each pair of conflict operations are ordered in the same way. Signup and view all the answers