86 lines
5.3 KiB
HTML
86 lines
5.3 KiB
HTML
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<?xml version="1.0" encoding="utf-8"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
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"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml" lang="en-US" xml:lang="en-us">
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<head>
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<meta name="dc.date" scheme="iso8601" content="2005-09-06" />
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<title>Adjust the WAN line speed for optimum iSeries server performance</title>
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<link rel="stylesheet" type="text/css" href="ibmidwb.css" />
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<link rel="stylesheet" type="text/css" href="ic.css" />
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<body>
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<a id="Top_Of_Page" name="Top_Of_Page"></a><!-- Java sync-link -->
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<script language = "Javascript" src = "../rzahg/synch.js" type="text/javascript"></script>
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<a name="rzajtper-wanlinfacts"></a>
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<h4 id="rzajtper-wanlinfacts">Adjust the WAN line speed for optimum iSeries server performance</h4>
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<p>In many cases, the communications line is the largest contributor to overall
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response time in the wide area network (WAN). Therefore, you should closely
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plan and manage its performance. In general, having the appropriate line speed
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is the key consideration for gaining the best performance.</p>
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<p>To adjust the line speed for your wide area network, perform these tasks:</p>
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<ul>
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<li>Check the difference in performance between half-duplex utilization and
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full-duplex utilization on the line description.</li>
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<li>For interactive environments, keep line use below 30% to maintain predictable
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and consistent response times. Exceeding 50% line use typically slows down
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response time. The line use can be measured with the iSeries™ system performance
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tools.</li>
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<li>For large transfer environments, or for environments in which only a small
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number of users are sharing a line, increase line use to allow for acceptable
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response times.</li>
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<li>The CPU usage for fractional T1 support and other high-speed WAN connections
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is similar to any other line that runs the same type of work. As the speed
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of a line increases from a traditional low speed to a high-speed or full T1/E1/J1
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speed, performance characteristics might change as follows:
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<ul>
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<li>With interactive transactions, performance might be slightly faster.</li>
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<li>With a large transfer, performance might be significantly faster.</li>
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<li>With a single job, performance might be too serialized to use the entire
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bandwidth.</li>
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<li>With high throughput, performance is more sensitive to frame size.</li>
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<li>With high throughput, performance is more sensitive to application efficiency.</li>
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<li>With synchronous data link control (SDLC), the communications controller
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CPU usage increases because of polling.</li></ul></li></ul>
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<p>Additional considerations for adjusting the wide area network line speed
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are the following:</p>
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<ul>
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<li>A common misconception about the line speed of each attached communications
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line is that the central processing unit (CPU) resource is used in a uniform
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fashion. Exact statements cannot be made about the number of lines that any
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given iSeries server model can support.</li>
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<li>Most communications applications use a lot of CPU resource (to process
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data, to support disk input and output) and communications line resource (to
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send and receive data or display I/O). The amount of line resource that is
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used is proportional to the total number of bytes that are sent or received
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on the line. Some additional CPU resource is used to process the communications
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software to support the individual sends (puts or writes) and receives (gets
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or reads). Communications input/output processor resource is also used to
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support the line activity.</li>
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<li>When a single job is running disk operations or doing non-overlapped CPU
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processing, the communications link is idle. If several sessions transfer
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concurrently, then the jobs are more interleaved and make better use of the
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communications link.</li>
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<li>Polling is an important consideration for synchronous data link control
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(SDLC) environments. All SDLC polling is handled by the communications controller
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and is governed by parameters in both the line and controller descriptions.</li></ul>
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<ul>
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<li>For information about iSeries system configuration, see the <a href="../books/c4154010.pdf" target="_blank">Communications Configuration</a>
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<img src="wbpdf.gif" alt="Link to PDF" /> book.</li>
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<li>For more information about performance tools, see the <a href="../books/sc415340.pdf" target="_blank">Performance Tools for iSeries</a>
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<img src="wbpdf.gif" alt="Link to PDF" /> book.</li></ul>
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