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Why Concurrency Control is required? Formal Concepts Serial, realizable, equivalent schedules 4 invalid schedules Concurrency control – a DBMS component Isolation levels ANSI SQL isolation levels Snapshot Isolation Locking Basics Deadlocks Index locking Optimistic locking Multi-Version Concurrency Control

A transaction is a program module that starts with ‘begin transaction’ statement, and execution ends in ‘commit transaction’ or ‘rollback transaction’. Syntax differs from one system to another normally includes its own computational statements (unbeknown to the DBMS) and requests for some database retrieval/update operations. is normally performed in an online environment: when ‘commit transaction’ statement returns, the updated data are effective immediately. when ‘rollback transaction’ statement returns, the effect of data modifications by the Xact will have been undone.

Topics: Data management with OS Data management with RDBMS Storage structures Row level operations B-tree Buffer management

Database I/O Systems