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<h1 class="topictitle1">Introduction to client/server performance</h1>
<div><p>The performance characteristics of a client/server environment
are different than those of centralized environments.</p>
<div class="section"><p>This is because client/server applications are split
between the client and the server. The client and server communicate by sending
and receiving requests and messages. This model is far different than that
for a centralized environment. In that environment, a program calls the CPU,
and the memory and disk drives are fully dedicated.</p>
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<div class="section"><p>Instead, when a client requests processing time and data from
the server, it transmits the request on the network. The request travels to
the server and waits in a queue until the server is able to process it. The
performance characteristics of this type of architecture degrade exponentially
as the number of requests increase. In other words, response times increase
gradually as more requests are made, but then increase dramatically at some
point, which is known as the "knee of the curve." This concept is illustrated
by the following graph:</p>
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<div class="section"><br /><img src="perf01.gif" alt="Client/server performance curve" /><br /></div>
<div class="section"><p>It is important to determine this point at which performance begins
to degrade significantly. The point can vary with every client/server installation.</p>
</div>
<div class="section"><p>The following is a suggested guideline for client/server operations: <em>Communicate
with the server only when necessary, and in as few data transmissions as possible.</em> Opening
a file and reading one record at a time often results in problems for client-server
projects and tools.</p>
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaikperftuneodbc.htm" title="A key consideration for ODBC application developers is achieving maximum performance from client/server applications.">Performance-tuning iSeries Access for Windows ODBC</a></div>
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