Thursday, 6 February 2020

Transaction Management


Transaction Management

? As transaction is the smallest unit of a work.
? It plays an important role in a Database Management System.
? In this unit we cover Properties of a transaction, Basic operations on transaction, State of
transaction etc. and cover Concepts of Concurrency Control and various problems which
occur on Concurrency such as Lost Updata problem, Dirty read problem etc. and cover
concepts about serializability along with a technique to find whether given transaction
are serial or not.

A transaction: This is a unit of program execution that accesses and possibly updates various
data items.
Aborted state: This transaction state occurs after the transaction has been rolled back and the
database has been restored to its state prior to the start of the transaction.
Active state: This is the initial state of a transaction, the transaction stays in this state while it is
starting execution.
Committed state: This transaction state occurs after the successful completion of the transaction.
Complete schedule: A schedule that contains either an abort or a commit statement for each
transaction whose actions are listed in schedule, then it is called a complete schedule. A complete
transaction must also contain all the actions of every transaction that appears in it.
Partially committed state: This transaction state occurs after the final (last) statement of the
transaction has been executed.

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