COM/COM+ QUESTIONS AND ANSWERS

1. Explain transaction atomicity.

We must ensure that the entire transaction is either
committed or rolled back.


2. Explain consistency.


We must ensure that the system is always left at the correct
state in case of the failure or success of a transaction.


3. Explain integrity.
Ensure data integrity by protecting concurrent transactions
from seeing or being adversely affected by each other's partial and
uncommitted results.


4. Explain durability.
Make sure that the system can return to its original state in
case of a failure.


5. Explain object pooling.


With object pooling, COM+ creates objects and keeps them in
a pool, where they are ready to be used when the next client makes a
request. This improves the performance of a server application that
hosts the objects that are frequently used but are expensive to
create.


6. Explain JIT activation.
The objective of JIT activation is to minimize the amount of
time for which an object lives and consumes resources on the server.
With JIT activation, the client can hold a reference to an object on
the server for a long time, but the server creates the object only
when the client calls a method on the object. After the method call is
completed, the object is freed and its memory is reclaimed. JIT
activation enables applications to scale up as the number of users
increases.


7. Explain role-based security.


In the role-based security model, access to parts of an
application are granted or denied based on the role to which the
callers belong. A role defines which members of a Windows domain are
allowed to work with what components, methods, or interfaces.


8. Explain queued components.


The queued components service enables you to create
components that can execute asynchronously or in disconnected mode.
Queued components ensure availability of a system even when one or
more sub-systems are temporarily unavailable. Consider a scenario
where salespeople take their laptop computers to the field and enter
orders on the go. Because they are in disconnected mode, these orders
can be queued up in a message queue. When salespeople connect back to
the network, the orders can be retrieved from the message queue and
processed by the order processing components on the server.


9. Explain loosely coupled events.


Loosely coupled events enable an object (publisher) to
publish an event. Other objects (subscribers) can subscribe to an
event. COM+ does not require publishers or subscribers to know about
each other. Therefore, loosely coupled events greatly simplify the
programming model for distributed applications.


10. Define scalability.


The application meets its requirement for efficiency even if
the number of users increases.


11. Define reliability.
The application generates correct and consistent information
all the time.


12. Define availability.


Users can depend on using the application when needed.


13. Define security.


The application is never disrupted or compromised by the
efforts of malicious or ignorant users.


14. Define manageability.


Deployment and maintenance of the application is as
efficient and painless as possible.


15. Which namespace do the classes, allowing you to support COM
functionality, are located?


System.EnterpriseServices

16. How do you make a NET component talk to a COM component?


To enable the communication between COM and .NET
components, the .NET Framework generates a COM Callable Wrapper (CCW).
The CCW enables communication between the calling COM code and the
managed code. It also handles conversion between the data types, as
well as other messages between the COM types and the .NET types.