63 lines
4.6 KiB
HTML
63 lines
4.6 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 name="DC.Type" content="concept" />
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<meta name="DC.Title" content="Read when logical file shares an access path with more keys operation" />
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<meta name="abstract" content="When the first-in-first-out (FIFO), last-in-first-out (LIFO), or first-changed-first-out (FCFO) keyword is not specified in the data description specifications (DDS) for a logical file, the logical file can implicitly share an access path that has more keys than the logical file being created." />
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<meta name="description" content="When the first-in-first-out (FIFO), last-in-first-out (LIFO), or first-changed-first-out (FCFO) keyword is not specified in the data description specifications (DDS) for a logical file, the logical file can implicitly share an access path that has more keys than the logical file being created." />
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<meta name="DC.subject" content="logical file, sharing access path, access path, sharing, key field, subset" />
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<meta name="keywords" content="logical file, sharing access path, access path, sharing, key field, subset" />
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<meta name="DC.Relation" scheme="URI" content="rbafordbrk.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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<link rel="stylesheet" type="text/css" href="./ibmdita.css" />
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<title>Read when logical file shares an access path with more keys operation</title>
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</head>
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<body id="rbafordlfksap"><a name="rbafordlfksap"><!-- --></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">Read when logical file shares an access path with more keys operation</h1>
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<div><p>When the first-in-first-out (FIFO), last-in-first-out (LIFO), or
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first-changed-first-out (FCFO) keyword is not specified in the data description
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specifications (DDS) for a logical file, the logical file can implicitly share
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an access path that has more keys than the logical file being created.</p>
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<div class="p">This sharing of a partial set of keys from an existing access path can
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lead to perceived problems for database read operations that use these partially
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shared keyed sequence access paths. The problems might appear to be: <ul><li>Records that should be read, are never returned to your program</li>
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<li>Records are returned to your program multiple times</li>
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</ul>
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</div>
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<p>What is actually happening is that your program or another currently active
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program is updating the physical file fields that are keys within the partially
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shared keyed sequence access path, but that are not actual keys for the logical
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file that is being used by your program (the fields being updated are beyond
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the number of keys known to the logical file being used by your program).
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The updating of the actual key fields for a logical file by your program or
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another program has always yielded the above results. The difference with
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partially shared keyed sequence access paths is that the updating of the physical
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file fields that are keys beyond the number of keys known to the logical file
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can cause the same consequences.</p>
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<p>If these consequences caused by partially shared keyed sequence access
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paths are not acceptable, the FIFO, LIFO, or FCFO keyword can be added to
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the DDS for the logical file, and the logical file created again.</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="rbafordbrk.htm" title="These read operations can be used with a keyed sequence access path to get database records.">Read database records using a keyed sequence access path</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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