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225 lines
8.7 KiB
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<?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>DB->set_lk_exclusive()</title>
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<link rel="stylesheet" href="apiReference.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="Berkeley DB C API Reference" />
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<link rel="up" href="db.html" title="Chapter 2. The DB Handle" />
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<link rel="prev" href="dbset_heap_regionsize.html" title="DB->set_heap_regionsize()" />
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<link rel="next" href="dbset_lorder.html" title="DB->set_lorder()" />
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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 11.2.5.3</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">DB->set_lk_exclusive()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="dbset_heap_regionsize.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2.
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The DB Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="dbset_lorder.html">Next</a></td>
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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="dbset_lk_exclusive"></a>DB->set_lk_exclusive()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB->set_lk_exclusive(DB *db, int nowait_onoff); </pre>
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<p>
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Configures the database handle to obtain a write lock on the
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entire database when it is opened. This gives the handle
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exclusive access to the database, because the write lock will block
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all other threads of control for both read and write access.
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</p>
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<p>
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Use this method to improve the throughput performance on your
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database for the thread that is controlling this handle. When
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configured with this method, operations on the database do not
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acquire page locks as they perform read and/or write operations.
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Also, the exclusive lock means that operations performed on the
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database handle will never be blocked waiting for lock due to
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another thread's activities. The application will also be immune to
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deadlocks.
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</p>
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<p>
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On the other hand, use of this method means that you can only
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have a single thread accessing the database until the handle is
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closed. For some applications, the loss of multiple threads
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concurrently operating on the database will result in
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performance degradation.
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</p>
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<p>
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Also, use of this method means that you can only have one
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transaction active for the handle at a time.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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This method is incompatible with the
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<a class="link" href="dbopen.html#open_DB_THREAD">DB_THREAD</a> configuration
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flag.
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</p>
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</div>
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<p>
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The <code class="methodname">DB->set_lk_exclusive()</code> method may
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not be called after the
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<a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a> method is called.
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</p>
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<p>
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The <code class="methodname">DB->set_lk_exclusive()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" 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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<h3 class="title"><a id="lk_exclusive_rep_notes"></a>Replication Notes</h3>
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</div>
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</div>
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</div>
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<p>
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Replication applications that use exclusive database handles
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need to be written with caution. This is because replication
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clients cannot process updates on an exclusive database until
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all local handles on the database are closed. Also, attempting
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to open an exclusive database handle on a currently operating
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client will result in the open call failing with the error
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<code class="literal">EINVAL</code>.
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</p>
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<p>
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Also, opening an exclusive database handle on a replication
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master will result in all clients being locked out of the
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database. On clients, existing handles on the exclusive
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database will return the error
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<code class="literal">DB_REP_DEAD_HANDLE</code> when accessed, and must
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be closed. New handles opened on the exclusive database will
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block until the master closes its exclusive database handle.
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</p>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp58420896"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp58421088"></a>nowait_onoff</h4>
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</div>
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</div>
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</div>
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<p>
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If set to <code class="literal">0</code>, this method will block
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until it can obtain the exclusive lock on the database. If
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set to some value other than <code class="literal">0</code>,
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<code class="literal">DB_LOCK_NOTGRANTED</code> is returned when the
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handle is opened if the exclusive database lock cannot be
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immediately obtained.
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</p>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp58399184"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DB->set_lk_exclusive()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" 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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<h4 class="title"><a id="idp58420256"></a>EINVAL</h4>
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</div>
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</div>
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</div>
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<p>
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If the method was called after
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<a class="xref" href="dbopen.html" title="DB->open()">DB->open()</a>
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was called; the method was called on a currently operating
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replication client; or if an invalid flag value or
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parameter was specified.
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</p>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp58425064"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a>
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</p>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp58430896"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="db.html#dblist" title="Database and Related Methods">Database and Related Methods</a>
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</p>
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</div>
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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="dbset_heap_regionsize.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="db.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="dbset_lorder.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">DB->set_heap_regionsize() </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"> DB->set_lorder()</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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