29-12-2012, 12:44 PM
Transaction Management
Transaction Management.ppt (Size: 327 KB / Downloads: 30)
Objectives
Function and importance of transactions.
Properties of transactions.
Concurrency Control
Meaning of serializability.
How locking can ensure serializability.
Deadlock and how it can be resolved.
How timestamping can ensure serializability.
Optimistic concurrency control.
Granularity of locking.
Recovery Control
Some causes of database failure.
Purpose of transaction log file.
Purpose of checkpointing.
How to recover following database failure.
Alternative models for long duration transactions.
Transaction Support
Transaction
Action, or series of actions, carried out by user or application, which reads or updates contents of database.
Logical unit of work on the database.
Application program is series of transactions with non-database processing in between.
Transforms database from one consistent state to another, although consistency may be violated during transaction.
Properties of Transactions
Four basic (ACID) properties of a transaction are:
Atomicity ‘All or nothing’ property.
Consistency Must transform database from one consistent state to another.
Isolation Partial effects of incomplete transactions should not be visible to other transactions.
Durability Effects of a committed transaction are permanent and must not be lost because of later failure.