81 lines
5.7 KiB
HTML
81 lines
5.7 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="security" content="public" />
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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="Update database records" />
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<meta name="abstract" content="The update operation allows you to change an existing database record in a logical or physical file." />
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<meta name="description" content="The update operation allows you to change an existing database record in a logical or physical file." />
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<meta name="DC.subject" content="updating, database record, record" />
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<meta name="keywords" content="updating, database record, record" />
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<meta name="DC.Relation" scheme="URI" content="rbafobasicop.htm" />
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<meta name="DC.Relation" scheme="URI" content="../rzakj/rzakjcommitkickoff.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbaforzahftra.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbaforzahfrca.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Rights.Owner" content="(C) Copyright IBM Corporation 1998, 2006" />
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<meta name="DC.Format" content="XHTML" />
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<meta name="DC.Identifier" content="rbafoupdbr" />
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<meta name="DC.Language" content="en-us" />
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<!-- All rights reserved. Licensed Materials Property of IBM -->
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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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<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>Update database records</title>
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</head>
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<body id="rbafoupdbr"><a name="rbafoupdbr"><!-- --></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">Update database records</h1>
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<div><p>The update operation allows you to change an existing database
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record in a logical or physical file. </p>
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<p> The UPDAT statement in the RPG/400<sup>®</sup> language and the REWRITE statement
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in the COBOL/400<sup>®</sup> language
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are examples of this operation. Before you update a database record, the record
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must first be read and locked. The lock is obtained by specifying the update
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option on any of the read operations listed under the <a href="rbafordbra.htm#rbafordbra">Read database records using an arrival sequence access path</a> or <a href="rbafordbrk.htm#rbafordbrk">Read database records using a keyed sequence access path</a>.</p>
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<div class="p">If you issue several read operations with the update option specified,
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each read operation releases the lock on the previous record before attempting
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to locate and lock the new record. When you do the update operation, the system
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assumes that you are updating the currently locked record. Therefore, you
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do not have to identify the record to be updated on the update operation.
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After the update operation is done, the system releases the lock. <div class="note"><span class="notetitle">Note:</span> The
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rules for locking are different if your job is running under commitment control. </div>
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</div>
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<p>If the update operation changes a key field in an access path for which
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immediate maintenance is specified, the access path is updated if the high-level
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language allows it. (Some high-level languages do not allow changes to the
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key field in an update operation.)</p>
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<p>If you request a read operation on a record that is already locked for
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update and if your job is running under a commitment control level of *ALL
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or *CS (cursor stability), then you must wait until the record is released
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or the time specified by the WAITRCD parameter on the create file or override
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commands has been exceeded. If the WAITRCD time is exceeded without the lock
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being released, an exception is returned to your program and a message is
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sent to your job stating the file, member, relative record number, and the
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job which has the lock. If the job that is reading records is not running
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under a commitment control level of *ALL or *CS, the job is able to read a
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record that is locked for update.</p>
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<p>If the file you are updating has an update trigger associated with it,
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the trigger program is called before or after updating the record.</p>
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<p>If the files being updated are associated with referential constraints,
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the update operation can be affected.</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="rbafobasicop.htm" title="These topics describe basic database file operations, including the read, update, write and delete operations.">Basic database file operations in programs</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="../rzakj/rzakjcommitkickoff.htm">Commitment control</a></div>
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<div><a href="rbaforzahftra.htm" title="A trigger is a set of actions that run automatically when a specified change or read operation is performed on a specified database file. On iSeries, you define a set of trigger actions in any supported high-level language.">Trigger automatic events in your database</a></div>
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<div><a href="rbaforzahfrca.htm" title="These topics discuss how to use referential constraints in your database to ensure that it contains only valid data.">Ensure data integrity with referential constraints</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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