Introduction to MTS
What is Microsoft Transaction Server?
- MTS is a middle-ware from Microsoft
- In a n-tire system middleware sits between your business components and client
application. It handles all the client requests for the components
- MTS is a component-based transaction processing system for building, deploying, and
administering internet and intranet server applications
- MTS manages resources like database connections, threads etc. for your components
What are main parts of systems built around MTS?
- Application components
- MTS executive
- Server processes
- Resource managers
- Resource dispensers
- MTS explorer
What are application components?
Application components are custom components that you design to suit your business
needs. These components are in-process (DLL) components which run under the control of MTS.
If you are designing components using VB you must make them as ActiveX DLLs with Apartment
What is MTS executive?
- MTS Executive is a DLL that provides run-time services for MTS components like thread
and context management
- This DLL loads into the processes that host application components and runs in the
What is server process ?
A server process is a system process that hosts the application components. A server
process can host multiple components.
What are resource managers ?
- A resource manager is a system service that manages transactional data with help of
- MTS supports resource managers that implement the OLE Transactions protocol e.g. MS-SQL
What are resource despensers ?
Resource dispensers manage system resources like database connections. MTS provides two
resource dispensers :
- ODBC/OLEDB Resource Dispenser
- Shared Property Manager
What is MS-DTC ?
Microsoft Distributed Transaction Coordinator is a system service that coordinates
transactions. With MS-DTC MTS can handle transactions spanning more than one machines.
MS-DTC uses a two-phase commit protocol for transaction management.
What is MTS explorer ?
MTS explorer is a GUI for managing and administrating MTS components
How to create transactional components?
There are two steps in creating transactional components.
- Inside your component you need to add code which tells MTS weather transaction is
completed successfully or not
- You need to set the transaction attribute of the component inside MTS - generally using
What is Object Pooling?
Object pooling is nothing but recycling a certain number of objects among clients
requesting them. The client requests for an object. If no instance of the object is
available MTS will create a new instanced and give it to the calling client. The client
will use the object and inform MTS when done with the help of special methods. MTS will
not immediately destroy the object but keep it in 'object pool'. The same instance of the
object is supplied to other clients requesting for the same component.
Presently (ver 2.0) MTS do not provide object pooling but Microsoft has promised it at
some later date. Microsoft has also provided some interfaces which you can use for this
forward compatibility. Currently, MTS simply creates and destroys objects rather than
What is Connection Pooling?
Connection pooling is similar to object pooling but it applies to database connections
instead of object instances. MTS does provides connection pooling.
Why MTS components are generally built stateless?
Because of object pooling feature of MTS clients are not guaranteed that between
different method calls they will get same object instance. Naturally, storing properties
or state in such objects is useless. MTS provides alternative mechanism of state
management called 'shared property manager'
What are transaction attributes of MTS components?
There are 4 transaction attributes in MTS :
- Requires a transaction : the objects require a transaction. If transaction do not exist
a new transaction is started
- Requires a new transaction : A new transaction is always started for the object
- Supports a transaction : The object uses a transaction context only if one already
- Does not support transaction : The object do not participate in transaction
You can set these attribute in MTS explorer or if you are working with VB6 you can set
the MTSTransactionMode property (which you can change later in MTS explorer)
How does a typical component is built with VB to work under MTS?
To create components with VB for MTS you should create ActiveX DLLs with apartment
threading model. The classes you create are similar to your normal class modules with some
limitations like :
- You should not use functions like MsgBox in the class as the class is running on server
and any call to such methods invokes the Msgbox at the server and not at the client
- You should avoid storing state i.e. properties because of object pooling feature of MTS(
presently MTS do not support true object pooling but Microsoft has promised it at later
A typical method will look like this :
Public Function Method1() As Boolean
On Error GoTo err_proc
Dim objcntxt As MTxAS.ObjectContext
Set objcntxt = GetObjectContext()
cnn.Execute "update authors set author='Bipin Joshi' where
Method1 = True
Method1 = False
In the above function calling setComplete or setAbort is important because it tells MTS
that you are finished with the object and the object can be recycled.
After you built the component you need to host it under the control of MTS using MTS