Transactional Component Services

1
Transactional Component Services

• Introduction of MTS 2.0
• -- by Ji Xu

2
What is MTS

• MTS stands for Microsoft Transaction Server.
• MTS is the best technology for building
  server-centered applications on Windows NT
• MTS simplifies the development and deployment of
  server-centered applications built using
  Microsoft Component Object Model (COM)
  technologies.
• MTS is ideal for developing line-of-business and
  electronic commerce applications with Web-based
  interfaces, leveraging powerful development tools
  for scalable, three-tiered development, and
  building production-quality applications with
  distributed object technologies.

3
Three-Tiered Computing

• Every application, from spreadsheets on
  personal computers to accounts payable systems on
  mainframes, has three components
• Presentation components focus on interacting with
  the user.
• Application logic components perform calculations
  and determine the flow of the application.
• Data components manage information that must
  persist across sessions, planned shutdowns, and
  systems failures.

4
2-Tiered vs. 3-Tiered

• 2-tiered architecture
  3-tiered architecture

5
2-Tiered vs. 3-Tiered (cont.)

• Reusing two-tiered application logic usually
  means cutting and pasting code between
  applications.
• Databases must maintain connections to each
  active client.
• To prevent corruption, once one client has asked
  for access to a specific piece of data, databases
  lock the data to prevent other clients from
  accessing the same data at the same time. Other
  clients must wait for the database to release the
  locks before they can proceed with their work.
• The security model used in two-tiered systems
  doesn't work well outside trusted LAN
  environments.

• Developers can develop reusable application
  components.
• Application components can share database
  connections.
• Access to resources are through native protocols
  and application interfaces instead of through
  data gateways. This improves performance and
  allows application owners to control access to
  their data.
• Middle-tiered application components can be
  secured centrally using a common infrastructure.
  Access can be granted or denied on a
  component-by-component basis, simplifying
  administration.

6
MTS Overview

• In MTS applications, application logic components
  run under the control of MTS on servers and are
  invoked by presentation-centered components
  running on clients through Microsoft's
  Distributed COM (DCOM) technologies. Clients can
  be a mixture of conventional applications and
  Active Server Page (ASP) scripts running within
  Microsoft Internet Information Server (IIS).
• Application logic components can access a number
  of different databases. Access to databases and
  resources is done through MTS Resource Dispensers
  that perform services such as connection pooling
  automatically. MTS also supports automatic
  transactions so that access to data and resources
  is done with all-or-nothing protection.

7
MTS application architecture

8
MTS Component Code Template

• Developers can build presentation and
  application logic components with any tool or
  programming language that can generate
  COM-compliant dynamic-link libraries (DLLs).

9
Transactions in MTS

• Consider a simple bank funds transfer
  application assembled from three components
  Transfer, Credit, and Debiteach built by a
  different developer.
• Credit adds an amount to a checking account
  database.
• Debit subtracts an amount from a savings account
  database.
• Transfer moves money from checking to savings by
  calling Credit and Debit.
• Assume that Transfer begins work by calling
  Debit and Credit. Debit succeeds and subtracts
  100 from a database. Credit fails because its
  database was unable to commit successfully.
  Unless the developer of Transfer has programmed
  what to do if one of the components has failed,
  the application will withdraw 100 from the
  savings account without putting it in a
  corresponding checking account.

10
Transaction in MTS (cont.)

• MTS makes transaction management transparent to
  the component developer.
• Developers can even use different tools and
  languages to build their components.
• They simply declare components to be
  transactional using the Transaction Server
  Explorer.
• When a component begins execution, MTS starts a
  transaction automatically if one is required.
• When the component accesses a resource such as a
  database, MTS automatically enlists the resource
  in the transaction. If the component calls
  another component, the called component also
  joins the transaction automatically.
• When all components in a transaction complete
  their work, MTS initiates a full two-phase commit
  to either commit or abort the work.

11
Transaction In MTS (cont.)
12
Summary

• MTS 2.0 is the easiest way to build and deploy
  COM-based applications on Windows NT. Developers
  can use popular development tools such as JAVA,
  C and Visual Basic.
• MTS 2.0 offers comprehensive component
  functionality, such as automatic transaction
  support, access to popular databases, message
  queuing products, and mainframe-based
  applications.
• MTS 2.0 is fully integrated with other Windows NT
  features for ease of Internet/intranet
  application development, Windows NT clustering
  services for fail over protection, MSMQ for
  reliable, loosely coupled communication, and the
  Windows NT security environment for simplified
  resource control.