68 lines
4.1 KiB
HTML
68 lines
4.1 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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<meta name="DC.Type" content="reference" />
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<meta name="DC.Title" content="Fenced or unfenced considerations" />
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<meta name="abstract" content="When creating a user-defined function (UDF) consider whether to make the UDF an unfenced UDF." />
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<meta name="description" content="When creating a user-defined function (UDF) consider whether to make the UDF an unfenced UDF." />
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<meta name="DC.subject" content="UDFs (User-defined functions), fenced versus unfenced" />
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<meta name="keywords" content="UDFs (User-defined functions), fenced versus unfenced" />
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<meta name="DC.Relation" scheme="URI" content="rbafywudfextern.htm" />
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<meta name="DC.Relation" scheme="URI" content="rbafyudfthreads.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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<title>Fenced or unfenced considerations</title>
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</head>
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<body id="rbafysqlpfenced"><a name="rbafysqlpfenced"><!-- --></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">Fenced or unfenced considerations</h1>
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<div><p>When creating a user-defined function (UDF) consider whether to
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make the UDF an unfenced UDF.</p>
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<div class="section"><p>By default, UDFs are created as fenced UDFs. Fenced indicates
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that the database should run the UDF in a separate thread. For complex UDFs,
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this separation is meaningful as it will avoid potential problems such as
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generating unique SQL cursor names. Not having to be concerned about resource
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conflicts is one reason to stick with the default and create the UDF as a
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fenced UDF. A UDF created with the NOT FENCED option indicates to the database
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that the user is requesting that the UDF can run within the same thread that
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initiated the UDF. Unfenced is a suggestion to the database, which can still
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decide to run the UDF in the same manner as a fenced UDF.</p>
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<pre><strong>CREATE FUNCTION</strong> QGPL.FENCED (parameter1 <strong>INTEGER</strong>)
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<strong>RETURNS INTEGER LANGUAGE SQL</strong>
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<strong>BEGIN
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RETURN</strong> parameter1 * 3;
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<strong>END</strong>;
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<strong>CREATE FUNCTION</strong> QGPL.UNFENCED1 (parameter1 <strong>INTEGER</strong>)
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<strong>RETURNS INTEGER LANGUAGE SQL NOT FENCED</strong>
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-- Build the UDF to request faster execution via the NOT FENCED option
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<strong>BEGIN</strong>
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<strong>RETURN</strong> parameter1 * 3;
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<strong>END</strong>;</pre>
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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="rbafywudfextern.htm" title="You can write the executable code of a UDF in a language other than SQL.">Write UDFs as external functions</a></div>
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</div>
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<div class="relref"><strong>Related reference</strong><br />
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<div><a href="rbafyudfthreads.htm" title="A UDF, defined as FENCED, runs in the same job as the SQL statement that called it. However, the UDF runs in a system thread, separate from the thread that is running the SQL statement.">Threads considerations</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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