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93 lines
3.5 KiB
93 lines
3.5 KiB
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>No Wait on Blocks</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
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<link rel="up" href="txnconcurrency.html" title="Chapter 4. Concurrency" />
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<link rel="prev" href="readmodifywrite.html" title="Read/Modify/Write" />
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<link rel="next" href="reversesplit.html" title="Reverse BTree Splits" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 12.1.6.2</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">No Wait on Blocks</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="readmodifywrite.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 4. Concurrency</th>
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<td width="20%" align="right"> <a accesskey="n" href="reversesplit.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="txnnowait"></a>No Wait on Blocks</h2>
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</div>
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</div>
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</div>
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<p>
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Normally when a DB transaction is blocked on a lock request, it
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must wait until the requested lock becomes available before its
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thread-of-control can proceed. However, it is possible to configure a
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transaction handle such that it will report a deadlock rather
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than wait for the block to clear.
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</p>
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<p>
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You do this on a transaction by transaction basis by specifying
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<span>
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<code class="literal">DB_TXN_NOWAIT</code>
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to the
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<code class="methodname">DbEnv::txn_begin()</code>
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method.
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</span>
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</p>
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<p>
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For example:
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</p>
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<pre class="programlisting"> DbTxn *txn = NULL;
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try {
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envp->txn_begin(NULL, &txn, DB_TXN_NOWAIT);
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...
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} catch (DbException &de) {
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// Deadlock detection and exception handling omitted
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// for brevity
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...</pre>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="readmodifywrite.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="txnconcurrency.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="reversesplit.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Read/Modify/Write </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Reverse BTree Splits</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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