136 lines
7.9 KiB
HTML
136 lines
7.9 KiB
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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<meta name="DC.Title" content="Database files and functions" />
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<meta name="abstract" content="When you create Unicode database applications, you need to consider the implications for creating physical files, creating logical files, and for database input/output." />
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<meta name="description" content="When you create Unicode database applications, you need to consider the implications for creating physical files, creating logical files, and for database input/output." />
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<meta name="DC.Relation" scheme="URI" content="rbagsobjlev65534and65535.htm" />
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<meta name="copyright" content="(C) Copyright IBM Corporation 1998, 2006" />
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<link rel="stylesheet" type="text/css" href="./ic.css" />
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<title>Database files and functions</title>
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</head>
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<body id="rbagsucs2dbfileconsid"><a name="rbagsucs2dbfileconsid"><!-- --></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">Database files and functions</h1>
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<div><p>When you create Unicode database applications, you need to consider
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the implications for creating physical files, creating logical files, and
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for database input/output.</p>
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<div class="section" id="rbagsucs2dbfileconsid__Header_186"><a name="rbagsucs2dbfileconsid__Header_186"><!-- --></a><h4 class="sectiontitle">Create physical files</h4><p>Unicode graphic
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fields can be created in physical files. This is done by specifying a G data
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type and a Unicode CCSID for the CCSID keyword.</p>
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<p>The following example
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shows the DDS for a physical file containing four fields, and the command
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for creating the file:</p>
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<pre>A R FMT1
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A EMPNO 6A
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A NAME 30G CCSID(1200)
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A DESCR1 500G CCSID(1200) VARLEN
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A DESCR2 500A
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CRTPF FILE(UNICODEPF) SRCFILE(CLR/QDDSSRC)</pre>
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<p>In the example:</p>
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<ul><li>The first field, <samp class="codeph">EMPNO</samp>, is a character field of length
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6. The CCSID of the EMPNO field is the SBCS CCSID of the job. The decision
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was made to use a character field because the EMPNO field contains only numerics
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and Unicode support is not needed.</li>
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<li>The <samp class="codeph">NAME</samp> and <samp class="codeph">DESCR1</samp> fields are both
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Unicode fields. Both of these fields may need to contain data from more than
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one EBCDIC code page so the decision was made to make these fields Unicode
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graphic.</li>
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<li>The <samp class="codeph">DESCR2</samp> field is the SBCS CCSID of the job. This field
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is used as illustration of mapping to a logical field in <a href="#rbagsucs2dbfileconsid__HDRCRTLF">Creating
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logical files</a>.</li>
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</ul>
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<p>You can specify the default (DFT) keyword for Unicode graphic fields.
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The default value can be specified as SBCS, bracketed-DBCS, or bracketed-DBCS-graphic
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character strings. If you do not specify the DFT keyword, the default value
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for fixed-length Unicode fields is the Unicode blank (hexadecimal 0020). For
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varying-length Unicode fields, the default is the empty string.</p>
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</div>
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<div class="section" id="rbagsucs2dbfileconsid__HDRCRTLF"><a name="rbagsucs2dbfileconsid__HDRCRTLF"><!-- --></a><h4 class="sectiontitle">Create logical files</h4><p>You can use logical
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files to map Unicode data to and from character, DBCS-open, or DBCS-graphic.
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This allows Unicode graphic data to be manipulated in a character based form.</p>
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<p>The
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following example shows the DDS for a logical file containing 4 character
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fields. The Unicode graphic data is converted to character data when reading
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from the logical file, and character data is converted to Unicode graphic
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data when writing to the file.</p>
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<pre>R FMT1 PFILE(UNICODEPF1)
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A EMPNO
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A NAME A CCSID(37)
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A DESCR1 A CCSID(37)
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A DESCR2 G CCSID(1200)</pre>
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</div>
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<div class="section" id="rbagsucs2dbfileconsid__Header_188"><a name="rbagsucs2dbfileconsid__Header_188"><!-- --></a><h4 class="sectiontitle">Database input/output</h4><p>Whenever reading
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or writing data from or to a field tagged with a Unicode CCSID to the job
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physical files, the data is passed as Unicode data without any conversions
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occurring. Regardless of the job CCSID, data is passed as Unicode data. When
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writing data to a logical file, the <em>from</em> CCSID is the job CCSID; however,
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if the job CCSID is 65535, the <em>from</em> CCSID is the CCSID of the field
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in the logical file.</p>
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<p>Here are some scenarios from the
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previous physical and logical files. For the scenarios, the job CCSID is 297.</p>
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<p><strong>Scenario
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1.</strong> When reading the data from the physical file:</p>
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<ul><li>EMPNO is converted from its CCSID to 297.</li>
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<li>NAME is not converted but is left as Unicode data.</li>
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<li>DESCR1 is not converted but is left as Unicode data.</li>
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<li>DESCR2 is converted from its CCSID to 297.</li>
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</ul>
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<p><strong>Scenario 2.</strong> When writing the data to the physical file:</p>
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<ul><li>EMPNO is converted from 297 to its CCSID.</li>
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<li>NAME is not converted but is left as Unicode data.</li>
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<li>DESCR1 is not converted but is left as Unicode data.</li>
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<li>DESCR2 is converted from 297 to its CCSID.</li>
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</ul>
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<p><strong>Scenario 3.</strong> When reading the data from the logical file:</p>
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<ul><li>EMPNO is converted from its CCSID to 297.</li>
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<li>NAME is converted from Unicode data to character data with a CCSID of
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297.</li>
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<li>DESCR1 is converted from Unicode data to character data with a CCSID of
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297.</li>
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<li>DESCR2 is converted from character data to Unicode data and not converted
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to the job CCSID.</li>
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</ul>
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<p><strong>Scenario 4.</strong> When writing the data to the logical file:</p>
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<ul><li>EMPNO is converted from 297 to its CCSID.</li>
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<li>NAME is converted from 297 to Unicode data.</li>
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<li>DESCR1 is converted from 297 to Unicode data.</li>
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<li>DESCR2 is converted from Unicodeto its CCSID in the physical file.</li>
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</ul>
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<p><strong>Scenario 5.</strong> If the job was 65535, the conversions for the previous
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fields are:</p>
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<ul><li>EMPNO is not converted.</li>
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<li>NAME is converted from 37 to Unicode data.</li>
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<li>DESCR1 is converted from 37 to Unicode data.</li>
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<li>DESCR2 is converted from Unicode to its CCSID in the physical file.</li>
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</ul>
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</div>
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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="rbagsucs2andas400.htm" title="i5/OS provides support for Unicode.">Unicode on i5/OS</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="rbagsobjlev65534and65535.htm" title="CCSID 65535 is the default object-level CCSID for message files and message queues.">Object-level coded character set identifier 65535</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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