200 lines
10 KiB
HTML
200 lines
10 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="reference" />
|
||
|
|
<meta name="DC.Title" content="DYNSLT (Dynamic Select) keyword—logical files only" />
|
||
|
|
<meta name="abstract" content="Use this file-level keyword to indicate that the selection and omission tests specified in the file (using select/omit specifications) are done at processing time. This keyword specifies dynamic select/omit rather than access path select/omit." />
|
||
|
|
<meta name="description" content="Use this file-level keyword to indicate that the selection and omission tests specified in the file (using select/omit specifications) are done at processing time. This keyword specifies dynamic select/omit rather than access path select/omit." />
|
||
|
|
<meta name="DC.subject" content="DYNSLT (Dynamic Select) keyword, Dynamic Select (DYNSLT) keyword" />
|
||
|
|
<meta name="keywords" content="DYNSLT (Dynamic Select) keyword, Dynamic Select (DYNSLT) keyword" />
|
||
|
|
<meta name="DC.Relation" scheme="URI" content="rzakbmstlfkeyw.htm" />
|
||
|
|
<meta name="copyright" content="(C) Copyright IBM Corporation 2001, 2006" />
|
||
|
|
<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 2001, 2006" />
|
||
|
|
<meta name="DC.Format" content="XHTML" />
|
||
|
|
<meta name="DC.Identifier" content="dtdynsl" />
|
||
|
|
<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>Physical and Logical Files, DYNSLT</title>
|
||
|
|
</head>
|
||
|
|
<body id="dtdynsl"><a name="dtdynsl"><!-- --></a>
|
||
|
|
<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
|
||
|
|
<h1 class="topictitle1">DYNSLT (Dynamic Select) keyword—logical files only</h1>
|
||
|
|
<div><p>Use this file-level keyword to indicate that the selection and
|
||
|
|
omission tests specified in the file (using select/omit specifications) are
|
||
|
|
done at processing time. This keyword specifies dynamic select/omit rather
|
||
|
|
than access path select/omit.</p>
|
||
|
|
<div class="section"><p>This keyword has no parameters.</p>
|
||
|
|
<p>When your program does input
|
||
|
|
operations to a logical file with the DYNSLT keyword specified, all the records
|
||
|
|
in the associated physical file are tested by the system to see if they satisfy
|
||
|
|
the select/omit values. Only those records that satisfy the values are supplied
|
||
|
|
to your program. The testing of each record can result in slower I/O performance,
|
||
|
|
but can be more efficient than maintaining an access path for the file. This
|
||
|
|
is particularly likely for files read only occasionally, especially when the
|
||
|
|
physical files they are based on are updated frequently. Using dynamic select/omit
|
||
|
|
is probably also more efficient for files with a high percentage of selected
|
||
|
|
records.</p>
|
||
|
|
<p>In
|
||
|
|
keyed sequence access files, an access path is created at file creation time
|
||
|
|
and is maintained for the file according to the MAINT parameter on the Create
|
||
|
|
Logical File (CRTLF) or Change Logical File (CHGLF) command. The DYNSLT keyword
|
||
|
|
does not affect the maintenance of access paths for keyed sequence access
|
||
|
|
files.</p>
|
||
|
|
<p>For all single-format logical files with a DYNSLT keyword, you
|
||
|
|
do not need to specify key fields in order to specify select/omit fields.
|
||
|
|
However, for all multiple-format logical files with a DYNSLT keyword, you
|
||
|
|
do need to specify at least one key field. You can specify *NONE for this
|
||
|
|
key field.</p>
|
||
|
|
<div class="p">You must use the DYNSLT keyword when you
|
||
|
|
want to select or omit fields and any of the following situations are true:
|
||
|
|
<ul><li>The logical file has arrival sequence (no key fields are specified). See
|
||
|
|
example 1 in this topic.</li>
|
||
|
|
<li>The logical file is a join logical file with the JDFTVAL keyword specified.</li>
|
||
|
|
<li>The logical file is a join logical file, select/omit fields come from
|
||
|
|
more than one of the physical files the logical file is based on, and one
|
||
|
|
of the following conditions is true: <ul><li>The select/omit fields are on the same select or omit statement. See example
|
||
|
|
3 in this topic.</li>
|
||
|
|
<li>The select/omit fields are on a mixture of select and omit statements.
|
||
|
|
See example 4 in this topic.</li>
|
||
|
|
<li>The select/omit fields are on select statements that are grouped together
|
||
|
|
by OR.</li>
|
||
|
|
<li>The select/omit fields are on omit statements that are grouped together
|
||
|
|
by AND.</li>
|
||
|
|
</ul>
|
||
|
|
</li>
|
||
|
|
</ul>
|
||
|
|
</div>
|
||
|
|
<p>You cannot specify the DYNSLT keyword with the REFACCPTH keyword.</p>
|
||
|
|
<p>For
|
||
|
|
a join logical file, the select/omit fields can occur in any of the physical
|
||
|
|
files specified on the JFILE keyword. Use the JREF keyword in join logical
|
||
|
|
files to qualify the origin of the field and resolve any ambiguities.</p>
|
||
|
|
</div>
|
||
|
|
<div class="section"><h4 class="sectiontitle">Examples</h4><p>The following examples show how to specify
|
||
|
|
the DYNSLT keyword.</p>
|
||
|
|
</div>
|
||
|
|
<div class="example"><h4 class="sectiontitle">Example 1</h4><p>The following example shows how to specify
|
||
|
|
dynamic select with arrival sequence.</p>
|
||
|
|
<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
|
||
|
|
00010A DYNSLT
|
||
|
|
00020A R RECORD1 PFILE(PF1)
|
||
|
|
00030A FLD1
|
||
|
|
00040A FLD2
|
||
|
|
00050A S FLD1 COMP(GT 2)</pre>
|
||
|
|
<p>The DYNSLT
|
||
|
|
keyword is required because there are no key fields.</p>
|
||
|
|
<div class="p">The logical file
|
||
|
|
supplies records to your program in arrival sequence. Assume that physical
|
||
|
|
file PF1 has the following records: <dl><dt><strong>FLD1</strong></dt>
|
||
|
|
<dd><strong>FLD2</strong></dd>
|
||
|
|
<dt class="dlterm">1</dt>
|
||
|
|
<dd>aaaa</dd>
|
||
|
|
<dt class="dlterm">2</dt>
|
||
|
|
<dd>dddd</dd>
|
||
|
|
<dt class="dlterm">3</dt>
|
||
|
|
<dd>jjjj</dd>
|
||
|
|
<dt class="dlterm">4</dt>
|
||
|
|
<dd>bbbb</dd>
|
||
|
|
</dl>
|
||
|
|
</div>
|
||
|
|
<div class="p">As your program does input operations, the system tests
|
||
|
|
the first two records according to the select/omit values, but does not supply
|
||
|
|
them to your program. Your program only sees the last two records: <dl><dt><strong>FLD1</strong></dt>
|
||
|
|
<dd><strong>FLD2</strong></dd>
|
||
|
|
<dt class="dlterm">3</dt>
|
||
|
|
<dd>jjjj</dd>
|
||
|
|
<dt class="dlterm">4</dt>
|
||
|
|
<dd>bbbb</dd>
|
||
|
|
</dl>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
<div class="example"><h4 class="sectiontitle">Example 2</h4><p>The following example shows how to specify
|
||
|
|
dynamic select with keyed sequence access path.</p>
|
||
|
|
<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
|
||
|
|
00010A DYNSLT
|
||
|
|
00020A R RECORD1 PFILE(PF1)
|
||
|
|
00030A FLD1
|
||
|
|
00040A FLD2
|
||
|
|
00050A K FLD1
|
||
|
|
00060A S FLD2 COMP(GT 'bbbb')
|
||
|
|
A</pre>
|
||
|
|
<div class="p">In this example, the DYNSLT keyword is not required.
|
||
|
|
The logical file supplies records to your program in keyed sequence. Assume
|
||
|
|
that physical file PF1 has the following records: <dl><dt><strong>FLD1</strong></dt>
|
||
|
|
<dd><strong>FLD2</strong></dd>
|
||
|
|
<dt class="dlterm">1</dt>
|
||
|
|
<dd>aaaa</dd>
|
||
|
|
<dt class="dlterm">2</dt>
|
||
|
|
<dd>dddd</dd>
|
||
|
|
<dt class="dlterm">3</dt>
|
||
|
|
<dd>jjjj</dd>
|
||
|
|
<dt class="dlterm">4</dt>
|
||
|
|
<dd>bbbb</dd>
|
||
|
|
</dl>
|
||
|
|
</div>
|
||
|
|
<div class="p">When your program requests a record, the system tests
|
||
|
|
the value of FLD2 for that record according to the select/omit values. Your
|
||
|
|
program only sees the following records: <dl><dt><strong>FLD1</strong></dt>
|
||
|
|
<dd><strong>FLD2</strong></dd>
|
||
|
|
<dt class="dlterm">2</dt>
|
||
|
|
<dd>dddd</dd>
|
||
|
|
<dt class="dlterm">3</dt>
|
||
|
|
<dd>jjjj</dd>
|
||
|
|
</dl>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
<div class="example"><h4 class="sectiontitle">Example 3</h4><p>The following example shows how to specify
|
||
|
|
a join logical file with select/omit comparing fields from two physical files.</p>
|
||
|
|
<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
|
||
|
|
00010A DYNSLT
|
||
|
|
00020A R RECORD1 JFILE(PF1 PF2)
|
||
|
|
00030A J JFLD(FLD1 FLD3)
|
||
|
|
00040A FLD1 JREF(PF1)
|
||
|
|
00050A FLD2 JREF(PF1)
|
||
|
|
00060A FLD3 JREF(PF2)
|
||
|
|
00070A FLD4 JREF(PF2)
|
||
|
|
00080A S FLD1 COMP(GT FLD4)
|
||
|
|
A</pre>
|
||
|
|
<p>FLD1 and FLD2 come from the primary file (PF1), and FLD3
|
||
|
|
and FLD4 come from the secondary file (PF2). The select specification compares
|
||
|
|
FLD1 from the primary file with FLD4 from the secondary file. Therefore, the
|
||
|
|
DYNSLT keyword is required.</p>
|
||
|
|
</div>
|
||
|
|
<div class="example"><h4 class="sectiontitle">Example 4</h4><p>The following example shows how to specify
|
||
|
|
a join logical file with select and omit using fields from more than one physical
|
||
|
|
file.</p>
|
||
|
|
<pre>|...+....1....+....2....+....3....+....4....+....5....+....6....+....7....+....8
|
||
|
|
00010A DYNSLT
|
||
|
|
00020A R JREC JFILE(PF1 PF2)
|
||
|
|
00030A J JOIN(PF1 PF2)
|
||
|
|
00040A JFLD(FLD1 FLD2)
|
||
|
|
00050A FLD1 JREF(PF1)
|
||
|
|
00060A FLD2 JREF(PF1)
|
||
|
|
00070A FLD3 JREF(PF2)
|
||
|
|
00080A K FLD1
|
||
|
|
00090A S FLD1 COMP(GT 0)
|
||
|
|
00100A O FLD3 COMP(GT 4)
|
||
|
|
A</pre>
|
||
|
|
<p>FLD1 and FLD3 come from different physical files and
|
||
|
|
are specified in a mixture of select and omit statements. Therefore, the
|
||
|
|
DYNSLT keyword is required.</p>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
<div>
|
||
|
|
<div class="familylinks">
|
||
|
|
<div class="parentlink"><strong>Parent topic:</strong> <a href="rzakbmstlfkeyw.htm" title="This topic lists valid keyword entries for describing physical and logical files. They are typed in positions 45 through 80 (functions).">Keyword entries for physical and logical files (positions 45 through 80)</a></div>
|
||
|
|
</div>
|
||
|
|
</div>
|
||
|
|
</body>
|
||
|
|
</html>
|