156 lines
10 KiB
HTML
156 lines
10 KiB
HTML
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<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE html
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PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html 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="copyright" content="(C) Copyright IBM Corporation 2005" />
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<meta name="DC.rights.owner" content="(C) Copyright IBM Corporation 2005" />
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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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<meta name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Record sequence and copying" />
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<meta name="abstract" content="The access path is the sequence in which records are organized in a database file. There are two types of access paths: keyed sequence and arrival sequence. With the copy function, you can process records in a database file in either arrival sequence or keyed sequence." />
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<meta name="description" content="The access path is the sequence in which records are organized in a database file. There are two types of access paths: keyed sequence and arrival sequence. With the copy function, you can process records in a database file in either arrival sequence or keyed sequence." />
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<meta name="DC.subject" content="access path, keyed sequence access path, arrival sequence access path, copying file, record sequence for, sequence of copied records, physical file, copying, sequence" />
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<meta name="keywords" content="access path, keyed sequence access path, arrival sequence access path, copying file, record sequence for, sequence of copied records, physical file, copying, sequence" />
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<meta name="DC.Relation" scheme="URI" content="rbal3bcfuc.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbal3selrecords.htm" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title> Record sequence and copying</title>
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</head>
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<body id="rbal3recsq"><a name="rbal3recsq"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1"> Record sequence and copying</h1>
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<div><p>The <dfn class="term">access path</dfn> is the sequence in which records are
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organized in a database file. There are two types of access paths: <dfn class="term">keyed
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sequence</dfn> and <dfn class="term">arrival sequence</dfn>. With the copy function,
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you can process records in a database file in either arrival sequence or keyed
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sequence.</p>
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<p>An arrival sequence copy transfers records in the order in
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which they physically exist in the from-file. Relative record numbers represent
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this order. The <dfn class="term">relative record number</dfn> is the position where
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the records physically exist in storage. Because records are always added
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to the end of the file, the relative record number represents the order in
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which records arrived in the file.</p>
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<p>A keyed sequence copy selects and transfers records by key value from a
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keyed physical file. This might result in a different physical order in the
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to-file. The to-file will be a reorganized version of the from-file. The relative
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record number of a specific record might change when a file is copied by key
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value:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" width="100%" frame="hsides" border="0" rules="none"><thead align="left"><tr><th align="center" valign="bottom" width="33.33333333333333%" id="d0e51">Relative record number</th>
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<th align="center" valign="bottom" width="33.33333333333333%" id="d0e53">Arrival sequence</th>
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<th align="center" valign="bottom" width="33.33333333333333%" id="d0e55">Keyed sequence</th>
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</tr>
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</thead>
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<tbody><tr><td align="center" valign="top" width="33.33333333333333%" headers="d0e51 ">1</td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e53 ">1011</td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e55 ">0016</td>
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</tr>
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<tr><td align="center" valign="top" width="33.33333333333333%" headers="d0e51 ">2 </td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e53 ">0762 </td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e55 ">0762 </td>
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</tr>
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<tr><td align="center" valign="top" width="33.33333333333333%" headers="d0e51 ">3 </td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e53 ">0810 </td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e55 ">0810 </td>
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</tr>
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<tr><td align="center" valign="top" width="33.33333333333333%" headers="d0e51 ">4</td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e53 ">3729</td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e55 ">1011</td>
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</tr>
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<tr><td align="center" valign="top" width="33.33333333333333%" headers="d0e51 ">5</td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e53 ">0016</td>
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<td align="center" valign="top" width="33.33333333333333%" headers="d0e55 ">3729</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>You can copy a keyed physical file in arrival sequence by specifying the
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FROMRCD or TORCD parameter on the COPY commands. When you do this, the keyed
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sequence access path is not used to retrieve the records in key sequence.
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The records are retrieved in arrival sequence. This is helpful when the physical
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relative record location in the file is significant and needs to remain the
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same as it is in the original file. Specifying FROMRCD(1) is a good way to
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copy all the records in arrival sequence. Copying a physical file in arrival
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sequence instead of keyed sequence is also faster.</p>
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<p>The kind of copy you run is determined by the type of from-file and the
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method of selecting records to copy. In general, files are copied using their
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keyed sequence, if they have one, otherwise, their arrival sequence.</p>
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<p>A copy from a keyed file to a keyed file typically places records at the
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end of the to-file in key field order, by the from-file key, regardless of
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their physical order in the from-file. But if you select records in the from-file
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by relative record number (using the FROMRCD or TORCD parameter), they are
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physically placed at the end of the to-file in relative record number order,
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regardless of their keyed sequence in the from-file. The following example
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shows the result of a COPY command that specifies from record 3 to record
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5:</p>
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<div class="tablenoborder"><table cellpadding="4" cellspacing="0" summary="" frame="border" border="1" rules="all"><thead align="left"><tr><th colspan="3" align="left" valign="top" id="d0e108">From-file</th>
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<th colspan="2" align="left" valign="top" id="d0e110">To-file</th>
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</tr>
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<tr><th align="left" valign="top" width="20%" id="d0e113">Relative record number</th>
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<th align="left" valign="bottom" width="20%" id="d0e115">Key</th>
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<th valign="top" width="17.77777777777778%" id="d0e117"> </th>
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<th align="left" valign="top" id="d0e118">Relative record number</th>
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<th align="left" valign="bottom" width="23.703703703703706%" id="d0e120">Key</th>
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</tr>
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</thead>
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<tbody><tr><td align="left" valign="top" width="20%" headers="d0e108 d0e113 ">1</td>
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<td align="left" valign="top" width="20%" headers="d0e108 d0e115 ">1011</td>
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<td valign="top" width="17.77777777777778%" headers="d0e108 d0e117 "> </td>
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<td align="left" valign="top" headers="d0e110 d0e118 ">.</td>
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<td align="left" valign="top" width="23.703703703703706%" headers="d0e110 d0e120 ">—</td>
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</tr>
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<tr><td align="left" valign="top" width="20%" headers="d0e108 d0e113 ">2</td>
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<td align="left" valign="top" width="20%" headers="d0e108 d0e115 ">0762</td>
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<td align="left" valign="top" width="17.77777777777778%" headers="d0e108 d0e117 "> </td>
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<td align="left" valign="top" width="18.51851851851852%" headers="d0e110 d0e118 ">.</td>
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<td align="left" valign="top" width="23.703703703703706%" headers="d0e110 d0e120 ">—</td>
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</tr>
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<tr><td align="left" valign="top" width="20%" headers="d0e108 d0e113 ">3</td>
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<td align="left" valign="top" width="20%" headers="d0e108 d0e115 ">0810</td>
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<td rowspan="3" align="left" valign="top" width="17.77777777777778%" headers="d0e108 d0e117 "> <p>< Arrival<br />
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< Sequence<br />
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< Copy</p>
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</td>
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<td align="left" valign="top" width="18.51851851851852%" headers="d0e110 d0e118 ">1401</td>
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<td align="left" valign="top" width="23.703703703703706%" headers="d0e110 d0e120 ">0810</td>
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</tr>
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<tr><td align="left" valign="top" width="20%" headers="d0e108 d0e113 ">4</td>
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<td align="left" valign="top" width="20%" headers="d0e108 d0e115 ">3729</td>
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<td align="left" valign="top" width="18.51851851851852%" headers="d0e110 d0e118 ">1402</td>
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<td align="left" valign="top" width="23.703703703703706%" headers="d0e110 d0e120 ">3729</td>
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</tr>
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<tr><td align="left" valign="top" width="20%" headers="d0e108 d0e113 ">5</td>
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<td align="left" valign="top" width="20%" headers="d0e108 d0e115 ">0016</td>
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<td align="left" valign="top" width="18.51851851851852%" headers="d0e110 d0e118 ">1403</td>
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<td align="left" valign="top" width="23.703703703703706%" headers="d0e110 d0e120 ">0016</td>
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</tr>
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</tbody>
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</table>
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</div>
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<p>When the to-file has a keyed sequence, the records appear in correct order
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in the to-file when using the keyed sequence access path. A copy by relative
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record number always copies by arrival sequence.</p>
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</div>
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<div>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbal3bcfuc.htm" title="You can copy from a physical or logical database file, open query file, diskette file, tape file, or inline data file. The to-file can be a physical database file, diskette file, tape file, program-described printer file, or *PRINT.">Copy files: basic functions</a></div>
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</div>
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<div class="relconcepts"><strong>Related concepts</strong><br />
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<div><a href="rbal3selrecords.htm" title="You can use parameters on the copy commands to select only the specific records that you want to copy.">Select the records to copy</a></div>
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</div>
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</div>
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</body>
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</html>
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