LSP4YOU - Learner's Support Publications

DBMS BCA Unit-5 Transaction - Definition Transaction - Examples COMMIT and ROLLBACK Properties of a Transaction States of Transactions The Concurrent Transactions Transactions - Lost Updates Transactions - Unrepeatable Reads Transactions - Dirty Reads Transactions - Inconsistent Analysis Serialisable Schedule Serial and Interleaved Schedule Precedence Graph Algorithm Precedence Graph Construction Non Serializable Schedule Locking Protocol Locks and Types of Locks Binary Locks Multiple-Mode Locks Shared and Exclusive Locks Two Phase Locking (2PL) Types of Two Phase Locking Database Security Goals Types of Database Security Threats to Databases Database Security & Authorization Subsystem Discretionary Security Mechanisms Mandatory Security Mechanisms Control Measures Access Control Inference Control Flow Control Data Encryption Database Security and the DBA DBA - Privileged Commands DBA Role Access Control, User Accounts and Database Audits System Log Database Audit Audit Trail Sensitive Data and Types of Disclosures Sensitive Data - Classification Factors Factors - Data is Safe Discretionary Access Control in a Database Account Level Privileges Relation Level Privileges Access Matrix Model Privileges on Relations

Locking Protocol

Concurrency related problems can be controlled by using locking. A lock is basically a variable that is associated with a data item in the database. A lock can be placed by a transaction on a shared resources that it desires to use. When this is done, the data item is available for the exclusive use for that transaction, i.e., other transactions are locked out of that data item. The transaction should unlock the data item after its use, for the use of other transactions.

The component of DBMS that controls and stores lock information is called the Lock Manager.
The locking mechanism helps us to convert a schedule into a serialisable schedule.