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COM and COM+ services and components in .NET questions
1) Explain
transaction atomicity. We must ensure that the entire
transaction is either committed or rolled back.
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.
Explain integrity. Ensure data integrity by protecting
concurrent transactions from seeing or being adversely
affected by each other’s partial and uncommitted results.
Explain
durability. Make sure that the system can return to its
original state in case of a failure.
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.
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.
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.
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.
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.
Define scalability. The application meets its requirement
for efficiency even if the number of users increases.
Define reliability. The application generates correct and
consistent information all the time.
Define availability. Users can depend on using the
application when needed.
Define security. The application is never disrupted or
compromised by the efforts of malicious or ignorant users.
Define manageability. Deployment and maintenance of the
application is as efficient and painless as possible.
Which namespace do the classes, allowing you to support COM
functionality, are located? System.EnterpriseServices
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. |
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