85 lines
5.4 KiB
HTML
85 lines
5.4 KiB
HTML
|
<?xml version="1.0" encoding="UTF-8"?>
|
||
|
|
<!DOCTYPE html
|
||
|
|
PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
||
|
|
<html lang="en-us" xml:lang="en-us">
|
||
|
|
<head>
|
||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
|
||
|
|
<meta name="security" content="public" />
|
||
|
|
<meta name="Robots" content="index,follow" />
|
||
|
|
<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))' />
|
||
|
|
<meta name="DC.Type" content="concept" />
|
||
|
|
<meta name="DC.Title" content="Choose compression type" />
|
||
|
|
<meta name="abstract" content="Choose compression type explains the types of compression that are available." />
|
||
|
|
<meta name="description" content="Choose compression type explains the types of compression that are available." />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="rzaiurzaiu290.htm" />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="../rzam4/rzam4overview.htm" />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="rzaiusavefiles.htm" />
|
||
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 2004, 2006" />
|
||
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2004, 2006" />
|
||
|
|
<meta name="DC.Format" content="XHTML" />
|
||
|
|
<meta name="DC.Identifier" content="compression" />
|
||
|
|
<meta name="DC.Language" content="en-us" />
|
||
|
|
<!-- All rights reserved. Licensed Materials Property of IBM -->
|
||
|
|
<!-- US Government Users Restricted Rights -->
|
||
|
|
<!-- Use, duplication or disclosure restricted by -->
|
||
|
|
<!-- GSA ADP Schedule Contract with IBM Corp. -->
|
||
|
|
<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
|
||
|
|
<link rel="stylesheet" type="text/css" href="./ic.css" />
|
||
|
|
<title>Choose compression type</title>
|
||
|
|
</head>
|
||
|
|
<body id="compression"><a name="compression"><!-- --></a>
|
||
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
||
|
|
<h1 class="topictitle1">Choose compression type</h1>
|
||
|
|
<div><p>Choose compression type explains the types of compression that
|
||
|
|
are available.</p>
|
||
|
|
<p>You can use compression and other capabilities to improve save performance
|
||
|
|
and also use less media for your save. Data compression compresses data on
|
||
|
|
the media when you perform the save operations. Data decompression reconstructs
|
||
|
|
data when you perform a restore operation. The system ensures that information
|
||
|
|
saved can be reconstructed exactly. No data is lost as a result of compression
|
||
|
|
and decompression.</p>
|
||
|
|
<p>The two main types of compression are hardware compression and software
|
||
|
|
compression. Most tape media devices use hardware compression, which is normally
|
||
|
|
faster than software compression. Software compression takes considerable
|
||
|
|
processing unit resources and may increase your save and restore time. </p>
|
||
|
|
<p>In addition to data compression, you can use compaction and optimum block
|
||
|
|
size features to streamline your save. These features are available through
|
||
|
|
parameters on all save commands: .</p>
|
||
|
|
<ul><li>Data Compression (DTACPR)</li>
|
||
|
|
<li>Data Compaction (COMPACT)</li>
|
||
|
|
<li>Use Optimum Block Size (USEOPTBLK)</li>
|
||
|
|
</ul>
|
||
|
|
<p>You can see examples of the parameter values in the <a href="../cl/savsys.htm">SAVSYS</a> command description. You can also find
|
||
|
|
more information about compression, compaction, and optimum block size in <a href="../books/sc410607.pdf" target="_blank">iSeries™ Performance Capabilities Reference</a><img src="wbpdf.gif" alt=" Link to PDF" /> </p>
|
||
|
|
<p>If you save to save files or optical media, you also have three choices
|
||
|
|
available for software compression: low, medium, and high. If you choose a
|
||
|
|
higher form of compression, your save will take longer, but the resulting
|
||
|
|
save data will usually be smaller. The following choices are available on
|
||
|
|
the Data Compression (DTACPR) parameter of the save commands and through the <a href="../apis/QsrSave.htm">Save Object (QsrSave</a>) and <a href="../apis/qsrsavo.htm">Save Object List (QSRSAVO)</a> APIs:</p>
|
||
|
|
<ul><li><span class="uicontrol">Low</span> — This is the default form of compression for
|
||
|
|
save files and optical media. Low compression is usually faster than medium
|
||
|
|
or high compression. The compressed data is usually larger than if medium
|
||
|
|
or high compression is used. </li>
|
||
|
|
<li><span class="uicontrol">Medium</span> — This is the default form of compression
|
||
|
|
for optical-DVD media. Medium compression is usually slower than low compression
|
||
|
|
but faster than high compression. The compressed data is usually smaller than
|
||
|
|
if low compression is used and larger than if high compression is used.</li>
|
||
|
|
<li><span class="uicontrol">High</span> — This form of compression is new at V5R2
|
||
|
|
and is meant to be used when maximum compression is desired. High compression
|
||
|
|
is usually noticeably slower than low and medium compression. The compressed
|
||
|
|
data is usually smaller than if low or medium compression is used.</li>
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
<div>
|
||
|
|
<div class="familylinks">
|
||
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzaiurzaiu290.htm" title="Read this information before you save anything on your server.">Before you save anything...</a></div>
|
||
|
|
</div>
|
||
|
|
<div class="relconcepts"><strong>Related concepts</strong><br />
|
||
|
|
<div><a href="rzaiusavefiles.htm">Save files</a></div>
|
||
|
|
</div>
|
||
|
|
<div class="relinfo"><strong>Related information</strong><br />
|
||
|
|
<div><a href="../rzam4/rzam4overview.htm">Storage Solutions</a></div>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
</body>
|
||
|
|
</html>
|