64 lines
4.3 KiB
HTML
64 lines
4.3 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="Enforcement of delete rules" />
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<meta name="abstract" content="When you delete a record from a parent file, the system checks the dependent file for any dependent records (matching non-null foreign key values). If the system finds any dependent records, the delete rule determines the action that is taken." />
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<meta name="description" content="When you delete a record from a parent file, the system checks the dependent file for any dependent records (matching non-null foreign key values). If the system finds any dependent records, the delete rule determines the action that is taken." />
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<meta name="DC.Relation" scheme="URI" content="rbaforzahfrcr.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="rbaforzahfrcs" />
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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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<!-- US Government Users Restricted Rights -->
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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>Enforcement of delete rules</title>
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</head>
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<body id="rbaforzahfrcs"><a name="rbaforzahfrcs"><!-- --></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">Enforcement of delete rules</h1>
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<div><p>When you delete a record from a parent file, the system checks
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the dependent file for any dependent records (matching non-null foreign key
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values). If the system finds any dependent records, the delete rule determines
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the action that is taken.</p>
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<div class="p"><ul><li><strong>No Action</strong>. If the system finds any dependent records, it returns
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a constraint violation and does not delete records.</li>
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<li><strong>Cascade</strong>. The system deletes dependent records that its finds in
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the dependent file.</li>
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<li><strong>Set Null</strong>. The system sets null-capable fields in the
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foreign key to null in every dependent record that it finds.</li>
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<li><strong>Set Default</strong>. The system sets all fields of the foreign key to their
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default value when it deletes the matching parent key.</li>
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<li><strong>Restrict</strong>. Same as no action except that enforcement is immediate.</li>
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</ul>
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</div>
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<p>If part of the delete rule enforcement fails, the entire delete operation
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fails and all associated changes are rolled back. For example, a delete cascade
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rule causes the database to delete ten dependent records, but a system failure
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occurs while deleting the last record. The database will not allow deletion
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of the parent key record, and the deleted dependent records are re-inserted.</p>
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<p>If a referential constraint enforcement causes a change to a record, the
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associated journal entry will have an indicator value noting that a referential
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constraint caused the record change. For example, a dependent record that
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is deleted by a delete cascade rule will have a journal entry indicator which
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indicates that the record change was generated during referential constraint
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enforcement. </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="rbaforzahfrcr.htm" title="The rules that you specify for the referential constraint determine how the database processes the delete and update operations on the parent key. The system enforces the unique attribute of a parent key on all parent file I/O.">Parent key enforcement</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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