Matakuliah : Web Database
Tahun
: 2008
Web Database Transaction
Session 11
Last Session Review:
•Physical Database Design
•Physical Web Database Design
•Web Architecture
•Client Processing
•Server Processing
•Java
•Implementation Choice
2
Agenda:
•Overview Transaction
•Incomplete or Abandoned Transaction
•Problem in Transaction
•Locking and Deadlock
•Web Database Transaction
3
Objectives:
•Student can understand about Transaction,
Incomplete or Abandoned Transaction, Problem in
Transaction, Locking and Deadlock and Web
Database Transaction
•Student can solve problem in transaction and
web database transaction
4
Overview Transaction
• What is Transaction?
– Sequence of instruction which alter the database so as to represent a single
change in the database, and/or which retrieve information about single
“snapshot” of the database to support some task
• What is Transaction Management?
– Ensures that each transaction satisfied certain validity properties so as to
provide safeguards to the data
• Validity properties:
–
–
–
–
Atomicity
Consistency
Independence
Durability
5
Incomplete or Abandoned Transaction
• What is Incomplete or Abandoned Transaction?
– Transaction that not completed due to failure or abandoned
• Cause of Failure?
–
–
–
–
Programming error
Hardware trouble
Network trouble
etc
• Cause of Abandoned?
– Browser Closed
– No resource to go next step (for application that use several steps)
– etc
6
Problem in Transaction
• Problem in Transaction?
– Lost Update
– Retrieval of Inconsistency Data
• How solve problems?
– Locking
7
Locking and Deadlock
• What is Locking?
– A means by which users can change parts of the database and no conflict with
one another
– Purpose of locks is to stop two (or more) users from trying to change the
same data at the same time, and also stops one user from update data while
it is being read by another user or being read while it is being updated
• Levels of Locking?
–
–
–
–
Tables locking
Rows locking
Individual objects locking
Type extents locking
8
Locking and Deadlock (cont.)
• Locking type that are support by commercial DBMS
– Read lock
– Write lock
– Upgrade lock
• Locking Protocols:
– Two Phase Locking
• Problem in Locking?
– Could end up in Deadlock
9
Locking and Deadlock (cont.)
• What is Deadlock?
– Two or more users are attempting to lock parts of the database and a cycle
occurs
• How to prevent Deadlock?
– Requiring each transaction to lock all the data it will needed when it starts 
optimistic locking
– Optimistic strategy by allowing deadlock to occur and then breaks the
deadlocks
– Ensuring that where possible each users access a copy of required data
• How to break Deadlock?
– Timeouts
10
Web Database Transaction
• Transaction in Web Database is more complex.
• One of the complexity is how to identifying a number of request as
parts of a single transaction from one user this is called “Session
Tracking”
• Technique to provide Session Tracking:
–
–
–
–
Hidden variables
URL rewriting
Cookies
User Authentication
11
Summary
• Implementation of Web Database Application should consider the
physical database design and physical web database design
• There is no one solution to every problem (no-silver-bullet). There
are lots of choice to implement web database application.
• Choose the right implementation by regarding several
considerations.
12
Next Session:
•Overview Security
•Database Security
•Web Security
•Client Security
•Efficiency vs Security
•Review of Session 8 - 13
13
End of
Web Database Transaction
Thank you
14