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.
