CUET Information practice (IP) Chapter 10 Fundamentals of Database

(c)

Exp: A Transaction is a logical unit of work that must succeed or fail in its entirety. It involves many sub-steps which should either all be carried out successfully or ignored if some failure occurs.

(c)

Exp: Transaction ends only when we use Commit or Rollback statement. Commit ends transaction by saving dataset changes, while Rollback ends transaction by discarding changes.

(a)

Exp: An atomic transaction cannot be subdivided and must be processed in its entirety or not at all. Atomicity means that users do not have to worry about the effect of incomplete transactions.

(b)

Exp: If you are reading a data item called X you need to write it down too. Read (X) operation brings data item A for execution in the main memory. Write (X) operation transfers data item B from main memory area to database file.

(a)

Exp: Atomicity is the property which ensures that either all operations of the transaction are reflected properly in the database or none are.

(c)

Exp: Durability is the property which ensures that after successful completion of a transaction, the changes made by it to the database persists even if there are system failures.

(a)

Exp: In the field of databases, a transaction log is a history of actions executed by a database management system to guarantee ACID properties over crashes or hardware failures. Physically, a log is a file of updates done to the database, stored in stable storage.

(c)

Exp: The transaction state is always in committed state after successful completion of particular transaction. Committed means whatever changes you have made to the transaction is saved permanently.

(b)

Exp: Transaction is the program which is used to make changes to the status of a database. A transaction is an action or a series of actions, which reads or updates the contents of a database.

(a)

Exp: Atomicity is the property which ensures that either all operations of the transaction are reflected properly in the database or none are. It makes the transaction atomic in nature, i.e., single unit of work.

(d)

Exp: Isolation is the property which implies that each transaction is unaware of other transactions executing concurrently in the system. This property makes a transaction relatively independent.

(b)

Exp: After successful completion of the process the transaction always is in consistent state.

(a)

Exp: The database system must have atomicity property to ensure integrity of data. Integrity is a concept of consistency of actions, values, methods, measures, principles, expectations and outcomes.

(c)

Exp: The COMMIT Statement terminates the current transaction and makes all changes under the transaction persistent. It commits the changes to the database. The COMMIT statement has the following general format:

COMMIT [WORK]

WORK is an optional keyword that does not change the semantics of COMMIT.

(c)

Exp: Durability is the property which ensures that after the successful completion of a Transaction, the changes made by it to the database persists, even if there are system failures.

(d)

Exp: The database system maintains the ACID property which comprises of Atomicity, Consistency, Isolation and Durability.

(a)

Exp: Transaction is always executed in two different ways:

Serially and concurrently. Concurrently is the simultaneous execution of multiple transaction.

(a)

Exp: A transaction gets divided into different segments by using SAVEPOINT for a specific segment. It saves the data at that point where it has been added in the transaction.

(a)

Exp: To perform all the operations into a transaction we need to implement it in between begin and end statement.

Also, we can use start statement to start the process.

BEGIN

/* Sql statements */

END

(b)

Exp: A transaction maintains ACID property to get integrity of the data. Data integrity means that data itself has a complete or whole structure. Data that has integrity is identically maintained during any operation (such as transfer, storage or retrieval).

(d)

Exp: Transaction always accesses the data into a database using read and write operation. Read is used for reading a data item and write is used for writing the data item.

(a)

Exp: In a computer or data transmission system, to abort means to terminate, usually in a controlled manner, a processing activity because it is impossible or undesirable for the activity to proceed. Once you have aborted a transaction, the transaction handle that you used for the transaction is no longer valid.

(a)

Exp: The committed or aborted transactions are called terminated which means the operation over that transaction is get completed or finished.

(a)

Exp: The Transaction is get executed by using two different methods:-

i) Serial

ii) Concurrent

Concurrent execution of the transaction is the concept which gets used in multiprogramming where multiple programs get executed simultaneously.

(a)

Exp: Data Manipulation Language (DML) is a family of computer languages used by computer programs and/or database users to insert, delete and update data in a database.

(d)

Exp: Commit is the command which is used to save the made changes permanent into the database.

(b)

Exp: To undo the changes that you have made within the database you need to apply Rollback command. After the Rollback command is issued, a new transaction is started implicitly by the database session.

(a)

Exp: If Transaction failure occurs then in that case any changes that you have made in the transaction is still undone.

(a)

Exp: This property ensures that either all operations of the transaction are reflected properly in the database or none are. This property ensures ”All-Or-None” operations are carried out.

(a)

Exp: Transaction Control unit is supported by the storage engines in mySql called InnoDB, NBD Cluster, BDB. These storage engines provide the large storage space.

(a)

Exp: Whenever you issue a DDL command or statement into the transaction it would call the commit statement implicitly.

(a)

Exp: To discard the changes that you have made to the database you can issue the Rollback statement. After the Rollback command is issued, a new transaction is started implicitly by the database session.

(b)

Exp: If you want to cancel the operation that you have performed over the database, then you can issue the command “Ctrl + Z”.

(b)

Exp: Rollback statement is used to discard the changes made to the database and a transaction is roll backed to the savepoint.

(a)

Exp: Autocommit is the property which is used to make each and every statement a transaction and is committed there and then.

(a)

Exp: To check the status of the autocommit property whether it is enabled or disabled you can issue the command

Mysql>Select @@autocommit;

It will give the output in terms of 0 or 1. 1 means that autocommit is currently enabled and 0 shows that it is disabled.

(c)

Exp: By default autocommit is enabled in MySQL. You can check the current setting by executing the following statement:

Mysql> select @@autocommit;

The @@ prefix denotes a server variable.

(a)

Exp: With autocommit enabled statement, every statement is wrapped within its own transaction. Successful execution of a statement is implicitly followed by COMMIT.

To disable the autocommit property you may write:

SET autocommit = 0;

This will disable the autocommit. And to enable it you may issue the command:-

SET autocommit = 1;

(a)

Exp: If you are in the middle of a transaction and a DDL command is executed, then the current transaction will be committed and ended implicitly.

(b)

Exp: SavePoint defines the breakpoints for the transaction to allow partial rollbacks. It divides the transaction into different sections or segments.

(a)

Exp: The System (database software) views a transaction as a logical sequence of read and write operations, where Read(X) operation brings data item X from the database to an area in the main memory where the transaction is executing. Write(X) operation transfers data item X from transaction’s main memory area to the database file.

(c)

Exp: TCL (Transaction Control Language) is the set of commands which is used for controlling the transaction operations. It is offered by the MySQL.

The TCL Consist of the following commands:

a· BEGIN|START TRANSACTION

b· COMMIT

c· ROLLBACK

d· SAVEPOINT

e· SET AUTOCOMMIT

(b)

Exp: Savepoint is a point in a transaction, until which all changes have been saved permanently. Savepoint are special operations that allow dividing work of a transaction into different segments.

(d)

Exp: A transaction is said to be complete or committed only if it has entered the committed state. A transaction is said to be in committed state after successful completion of operation.

(b)

Exp: A transaction enters the failed state after the system determines that the transaction can no longer proceed with its normal execution. Such a transaction must be rolled back.

(c)

Exp: A database transaction comprises a unit of work performed within a database management system (or similar system) against a database and treated in a coherent and reliable way independent of other transactions.

(b)

Exp: A database is a collection of interrelated data stored together to serve multiple applications.

(a)

Exp: DML stands for Data Manipulation Language. It provides commands to insert, delete and modify tuples in the database.

(b)

Exp: The keyword work is optional in both the statements.

(a)

Exp: Transactions are required to have the ACID properties: atomicity, consistency, isolation and durability.