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

Serialisable Schedule

A schedule S of n transactions is serialisable if it is equivalent to some serial schedule of the same ‘n’ transactions.

A serial schedule is a schedule in which either transaction T1 is completely done before T2 or transaction T2 is completely done before T1.

Any schedule that produces the same results as a serial schedule is called a serialisable schedule.

There are two possible serial schedule in case of two transactions (T1 and T2). That is T1-T2 or T2-T1. Similarly, in case of three parallel transactions the number of possible serial schedule is 3!, that is 6.

These serial schedules can be:
T1-T2-T3	T1-T3-T2
T2-T1-T3	T2-T3-T1
T3-T1-T2	T3-T2-T1