144 lines
8.6 KiB
HTML
144 lines
8.6 KiB
HTML
<?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 http-equiv="Content-Type" content="text/html; charset=utf-8" />
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<meta name="dc.language" scheme="rfc1766" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<!-- US Government Users Restricted Rights -->
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<!-- Use, duplication or disclosure restricted by -->
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<!-- GSA ADP Schedule Contract with IBM Corp. -->
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<meta name="dc.date" scheme="iso8601" content="2005-10-03" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="security" content="public" />
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<meta name="Robots" content="index,follow"/>
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<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
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<title>Performance considerations for APPN and HPR</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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</head>
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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="rzahjper-comappnfacts"></a>
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<h3 id="rzahjper-comappnfacts">Performance considerations for APPN and HPR</h3>
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<p>The following can affect the performance of the APPN and HPR protocols:</p>
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<ul>
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<li>Transmission priority
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<p>When you create a class-of-service description,
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you can define one of three transmission priorities for each class of service.
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You can specify, using the transmission priority (TMSPTY) parameter, that
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the transmission priority for any class of service is high, medium, or low.</p>
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<p>The transmission priority you specify is carried in the session activation
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request at session establishment. The transmission priority allows each logical
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unit on the session and each routing entry along the session path to store
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the same transmission priority. By assigning an appropriate mode (which includes
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a class of service) at session activation time, you can ensure a better response
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time for the applications that require it. Generally, interactive traffic
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should have a high priority and batch traffic a low priority.</p></li>
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<li>Route addition resistance
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<p>Route addition resistance (RAR) is a relative
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value that indicates how desirable one network node is, as compared to other
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network nodes, for having intermediate sessions routed through it.</p>
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<p>Changing this value and working with the different class-of-service descriptions
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can control route sessions.</p>
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<p>The RAR value is defined in the network
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attributes for the local iSeries system.</p></li>
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<li>Pacing values: See <a href="rzahjperpacingfacts.htm#rzahjper-pacingfacts">Pacing (INPACING,
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OUTPACING, MAXINPACING) parameters</a> for pacing considerations.</li>
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<li>Session activation considerations
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<p>When a session is requested to a remote
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location that matches a network node control-point name, a directory search
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is not performed by the node that calculates the route. This is true if the
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session request is being started by a user on the network node, or on an end
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node that the network node is providing services for. Session start requests
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for remote locations in end nodes and remote locations in network nodes that
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do not match the control-point name of the network nodes take longer. These
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session start requests take longer because the directory search needs to be
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sent and the replies need to be received.</p></li>
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<li>Maximum intermediate sessions
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<p>The Change Network Attributes (CHGNETA)
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command specifies the maximum number of intermediate sessions that are allowed
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on a network node. When the number of intermediate sessions reaches 90% of
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the maximum value, the node is marked as congested. A node that is congested
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may or may not be used for intermediate sessions that depend on the class-of-service
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definition. The node is not congested when the number of intermediate sessions
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drops below 80% of the configured value. Also, if the maximum number of intermediate
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sessions is reached (100%), then intermediate sessions will not be allowed
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through this network node until the value drops. You can limit the effect
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of intermediate sessions on local processing by setting an appropriate value.</p></li>
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<li>Segmentation and reassembly
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<p>On iSeries™, some IOPs that support the local area
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network protocols, such as token ring and Ethernet, have the ability to perform
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segmentation and reassembly of SNA Request Units. Performing this function
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in the IOPs offloads this work from the server CPU. The server CPU is free
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to perform other tasks.</p>
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<a name="wq89"></a>
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<div class="notetitle" id="wq89">Note:</div><img src="delta.gif" alt="Start of change" />
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<div class="notebody">Communications input/output
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adapters (IOAs), such as Gigabit Ethernet, do not require an input/output
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processor (IOP) and therefore perform segmentation in the server CPU. Gigabit
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Ethernet adapters do not automatically support SNA. Enterprise Extender (or AnyNet®) is required to allow SNA data to flow over a Gigabit adapter. IBM® recommends
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that Enterprise Extender be used in place of AnyNet.</div><img src="deltaend.gif" alt="End of change" />
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<p><img src="delta.gif" alt="Start of change" />With
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APPN, any network congestion control is handled on a hop-by-hop basis by using <a href="rzahjperpacingfacts.htm#rzahjper-pacingfacts">pacing </a> values. It is possible to over-drive
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connections in an APPN environment. A particular system might receive more
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data over a communications link than it can handle based on buffer space.
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The system requires the node that sends the data to retransmit all of the
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frames that were sent following the last successfully acknowledged frame.
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This retransmission occurs at the data link control (DLC) layer.</p>
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<a name="wq90"></a>
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<div class="notetitle" id="wq90">Note:</div>
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<div class="notebody">HPR has little IOP assistance. Much of the segmentation and reassembly is
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done in the server CPU.</div><img src="deltaend.gif" alt="End of change" /></li>
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<li>Error recovery
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<p>APPN requires link-level error recovery to cause retransmission
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of lost frames. This link-level error recovery can only survive short and
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temporary outages (several seconds). If a link outage or node outage occurs,
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that is of longer duration, APPN has no recovery mechanisms for keeping the
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affected sessions active. The applications must handle any session recovery.</p>
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<p>The following matrix shows how HPR traffic is supported between two
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systems that are based on their HPR link-level error recovery settings. The
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HPR link-level error settings are exchanged between the systems: </p><img src="delta.gif" alt="Start of change" />
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<a name="wq91"></a>
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<table id="wq91" width="90%" summary="" border="1" frame="border" rules="all">
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<tbody valign="top">
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<tr>
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<td width="29%" rowspan="2" align="left" valign="top"><span class="bold">System 1</span></td>
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<td colspan="3" align="left" valign="top"><span class="bold">System 2</span></td>
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</tr>
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<tr>
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<td width="24%" align="left" valign="top">No link-level ERP allowed</td>
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<td width="23%" align="left" valign="top">Link-level ERP required</td>
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<td width="22%" align="left" valign="top">Prefer no link-level ERP but might run using
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link-level ERP</td>
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</tr>
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<tr>
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<td align="left" valign="top">No link-level ERP allowed</td>
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<td align="left" valign="top">HPR supported (no ERP)</td>
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<td align="left" valign="top">HPR not used</td>
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<td align="left" valign="top">HPR supported (no ERP)</td>
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</tr>
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<tr>
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<td align="left" valign="top">Link-level ERP required</td>
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<td align="left" valign="top">HPR not used</td>
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<td align="left" valign="top">HPR supported (uses ERP)</td>
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<td align="left" valign="top">HPR supported (uses ERP)</td>
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</tr>
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<tr>
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<td align="left" valign="top">Prefer no link-level ERP but might run using
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link-level ERP</td>
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<td align="left" valign="top">HPR supported (no ERP)</td>
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<td align="left" valign="top">HPR supported (uses ERP)</td>
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<td align="left" valign="top">HPR supported (no ERP)</td>
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</tr>
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</tbody>
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</table><img src="deltaend.gif" alt="End of change" /></li></ul>
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<p>For information about high-performance routing, see <a href="rzahjpercomhprfacts.htm#rzahjper-comhprfacts">Optimize communications using high-performance routing</a>.</p>
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<a id="Bot_Of_Page" name="Bot_Of_Page"></a>
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</body>
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</html>
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