DB Quiz 9

Deferred updates

Using __________ ________, writes are done initially to the log only and the log records are used to perform actual updates to the database.

Immediate updates

Using ___________ ________, an update may be made to the database itself any time after a log record is written. The log can be used to undo and redo transactions in the event of failure.

Commit Rollback

What are the two ways to complete a transaction?

Tree

A ______ may be used to represent the granularity of locks in a system that allows locking of data items of different sizes.

Serializable

A schedule is __________ if it produces the same results as some serial schedule.

Two-phase locking (2pl)

A transaction acquires all its locks before releasing any

Work

A transaction is a logical unit of _______ that takes the database from one consistent state to another.

Atomicity, consistency, isolation, and durability

A transaction should possess the four basic or so-called ACID properties:

Rollback

Aborted transactions must be undone or.....

Transaction

Action, or series of actions, carried out by a single user or application program, that accesses or changes the contents of the database.

Advanced transaction models

Include nested transactions, sagas, multilevel transactions, dynamically restructuring transactions, and workflow models.

SAVEPOINT

MySQL enables you to perform a partial rollback of a transaction. To do this, issue a ____________ statement within the transaction to set a marker.

Deadlock

Occurs when two or more transactions are waiting to access data the other transaction has locked. The only way to break __________ once it has occurred is to abort one or more of the transactions.

Concurrency control

Process of managing simultaneous operations on the database without having them interfere with one another.

Database recovery

Process of restoring the database to a correct state after a failure. Both protect the database from inconsistencies and data loss.

Schedule

Shows the sequence of the operations of transactions

1. SET AUTOCOMMIT = 0; 2. START TRANSACTION; 3. INSERT, UPDATE, DELETE statements 4. SAVEPOINT name; 5. COMMIT or ROLLBACK

Steps to using InnoDB

InnoDB

Storage engine for MySQL; default since MySQL 5.5

Concurrency Recovery

The transaction is also the unit of ____________ and _________.

Log file

To facilitate recovery, one method is for the system to maintain a _____ _____, containing transaction records that identify the start/end of transactions and the before- and after-images of the write operations.

Intention

To show whether any of the node's descendants are locked, an _________ lock is placed on all the ancestors of any node being locked.

Timestamping

Transactions are ordered in such a way that older transactions get priority in the event of conflict.

Abort

Transactions can terminate UNsuccessfully, which is called?

Commit

Transactions can terminate successfully, which is called?

True

True or False? If the system fails, it examines the log to determine which transactions it needs to redo, but there is no need to undo any writes.

True

True or False? When a new transaction requests a lock, it is easy to check all the ancestors of the object to determine whether they are already locked.

True

True or False? When an item is locked, all its descendants are also locked.

Two-phase locking (2pl) Timestamping

Two methods that guarantee serializability are:

Checkpoint

Used to improve database recovery. At a ___________, all modified buffer blocks, all log records, and a ____________ record identifying all active transactions are written to disk. If a failure occurs, the ____________ record identifies which transactions need to be redone.

Concurrency control

______________ ________ is needed when multiple users are allowed to access the database simultaneously.