63 lines
4.6 KiB
HTML
63 lines
4.6 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="Dynamic select/omit" />
|
||
|
|
<meta name="abstract" content="With the dynamic select/omit operation, when a program reads records from the file, the system only returns those records that meet the select/omit values. That is, the actual select/omit processing is done when records are read by a program, rather than when the records are added or changed." />
|
||
|
|
<meta name="description" content="With the dynamic select/omit operation, when a program reads records from the file, the system only returns those records that meet the select/omit values. That is, the actual select/omit processing is done when records are read by a program, rather than when the records are added or changed." />
|
||
|
|
<meta name="DC.subject" content="dynamic select/omit, select/omit, dynamic" />
|
||
|
|
<meta name="keywords" content="dynamic select/omit, select/omit, dynamic" />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="rbafosorec.htm" />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="rbafoshrap.htm" />
|
||
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
|
||
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
|
||
|
|
<meta name="DC.Format" content="XHTML" />
|
||
|
|
<meta name="DC.Identifier" content="rbafoapdyn" />
|
||
|
|
<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>Dynamic select/omit</title>
|
||
|
|
</head>
|
||
|
|
<body id="rbafoapdyn"><a name="rbafoapdyn"><!-- --></a>
|
||
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
||
|
|
<h1 class="topictitle1">Dynamic select/omit</h1>
|
||
|
|
<div><p>With the dynamic select/omit operation, when a program reads records
|
||
|
|
from the file, the system only returns those records that meet the select/omit
|
||
|
|
values. That is, the actual select/omit processing is done when records are
|
||
|
|
read by a program, rather than when the records are added or changed. </p>
|
||
|
|
<p>However, the keyed sequence access path contains all the keys, not just
|
||
|
|
keys from selected records. Access paths using dynamic select/omit allow more
|
||
|
|
access path sharing, which can improve performance. </p>
|
||
|
|
<p>To specify dynamic select/omit,
|
||
|
|
use the dynamic selection (DYNSLT) keyword. With dynamic select/omit, key
|
||
|
|
fields are not required.</p>
|
||
|
|
<p>If you have a file that is updated frequently and read infrequently, you
|
||
|
|
might not need to update the access path for select/omit purposes until your
|
||
|
|
program reads the file. In this case, dynamic select/omit might be the correct
|
||
|
|
choice. The following example helps describe this.</p>
|
||
|
|
<p>You use a code field (A=active, I=inactive), which is changed infrequently,
|
||
|
|
to select/omit records. Your program processes the active records
|
||
|
|
and the majority (over 80%) of the records are active. It can be more efficient
|
||
|
|
to use DYNSLT to dynamically select records at processing time rather than
|
||
|
|
perform access path maintenance when the code field is changed.</p>
|
||
|
|
</div>
|
||
|
|
<div>
|
||
|
|
<div class="familylinks">
|
||
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rbafosorec.htm" title="The system can select and omit records when using a logical file. This can help you exclude records in a file for processing convenience or for security.">Select and omit records using logical files</a></div>
|
||
|
|
</div>
|
||
|
|
<div class="relconcepts"><strong>Related concepts</strong><br />
|
||
|
|
<div><a href="rbafoshrap.htm" title="When two or more files are based on the same physical files and the same key fields in the same order, they automatically share the same keyed sequence access path. When access paths are shared, the amount of system activity required to maintain access paths and the amount of auxiliary storage used by the files is reduced.">Use existing access paths</a></div>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
</body>
|
||
|
|
</html>
|