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Click
here for a Flash overview of RDA Push and Pull
If you haven't had any experience yet
with SQL Server CE, I am sure you will be hooked before
you complete your first application. It is an incredible
solution for mobile database needs, which offers real performance
and scalability.
So...
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Introduction
SQL Server CE provides two methods
for SQL Server (desktop) data access.
The first is Replication.
"Merge replication
in SQL Server CE is based on Microsoft SQL Server 2000
merge replication and is ideally suited to portable devices
because it enables data to be updated independently on the
portable device and the server. The data on the device and
the server can later be synchronized when the device is
connected to the server."
-Microsoft Books Online
One would use replication when the
solution requires that any data modification must be maintained
on both the handheld and desktop - such as an inventory
tracking system.
The second method, is Remote Data Access
(RDA).
"Remote data access
(RDA) provides a simple way for a Windows CE application
to access SQL Server data located in a remote SQL Server
6.5, SQL Server 7.0, or SQL Server 2000 database. RDA can
be used whether the Windows CE device is continuously connected
or intermittently connected to the SQL Server system. Applications
use RDA when they do not need the full functionally of merge
replication. You can use RDA without configuring SQL Server
replication or creating publications."
-Microsoft Books Online
That is not to say that RDA is
a 'poor relative' of Merge Replication. RDA is a great tool
to use when only portions of a database need to be transferred
to the handheld, and/or a constant sync state is not a priority.
As an example: School
administrators want to be able to carry student demographic
and emergency contact information around with them - on
their handhelds. The data needs to be current, but they
wouldn't be making any changes to the records. In this case,
Merge Replication wouldn't be necessary - and a simple RDA
'pull' gets the job done. If RDA is all you need, this article
is for you.
How it is Done
Remote Data Access on CE handhelds
is implemented by a few dll's, a relay agent, IIS and SQL
Server. Each piece has its own job, and putting them together
can present an issue if you aren't familiar with how they
work together. Take a look at this flash
animation to see how all the pieces work together.
This Project
You should be able to get this project
put together in about an hour following these ten steps.
Remember that configuration is everything! If any of your
settings are incorrect your project won't work - and it
will be difficult to pinpoint the problem. Error messages
(if you manage to get one) are usually very vague and may
only be the symptom of an earlier error. I have included
a list of my top five blunders for your benefit.
I would like to thank TechSmith,
makers of Camtasia for making this article possible. I used
Camtasia to record movie clips that detail each configuration
step - which I hope will guide you through the development
process, and help you avoid common mistakes. I highly recommend
it for anyone that needs to put instructional presentations
together. It's easy to use, and very inexpensive.
All you need is TechSmith's
Video Codec for Windows Media Player.
This project was constructed
with eVB
3.0, Windows 2000, SQL Server 2000, SQL
Server CE, SQL Server CE Relay, Active
Sync 3.1, IIS and uses an Anonymous authentication method.
Please make sure you have all these items before you start.
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