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HTML
227 lines
10 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_ENV->close()</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="env.html" title="Chapter 5. The DB_ENV Handle" />
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<link rel="prev" href="envadd_data_dir.html" title="DB_ENV->add_data_dir()" />
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<link rel="next" href="envcreate.html" title="db_env_create" />
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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 11.2.5.2</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">DB_ENV->close()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="envadd_data_dir.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5.
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The DB_ENV Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="envcreate.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="envclose"></a>DB_ENV->close()</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_ENV->close(DB_ENV *dbenv, u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB_ENV->close()</code> method closes the
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Berkeley DB environment, freeing any allocated resources and
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closing all database handles opened with this environment handle,
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as well as closing any underlying subsystems.
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</p>
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<p>
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When you call the <code class="methodname">DB_ENV->close()</code> method,
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all open <a class="link" href="db.html" title="Chapter 2. The DB Handle">DB</a> handles and
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<a class="link" href="dbc.html" title="Chapter 3. The DBcursor Handle">DBcursor</a> handles are closed
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automatically by this function. And, when you close a database
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handle, all cursors opened with it are closed automatically.
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</p>
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<p>
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In multiple threads of control, each thread of control opens a
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database environment and the database handles within it. When you
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close each database handle using the
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<code class="methodname">DB_ENV->close()</code> method, by default, the
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database is not synchronized and is similar to calling the
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<code class="methodname">DB->close(DB_NOSYNC)</code> method. This is to
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avoid unncessary database synchronization when there are multiple
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environment handles open. To ensure all open database handles are
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synchronized when you close the last environment handle, set the
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flag parameter value of the <code class="methodname">DB_ENV->close()</code>
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method to DB_FORCESYNC. This is similar to calling the
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<code class="methodname">DB->close(0)</code> method to close each database
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handle.
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</p>
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<p>
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If a database close operation fails, the method returns a non-zero
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error value for the first instance of such an error, and continues
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to close the rest of the database and environment handles.
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</p>
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<p>
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The <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle should
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not be closed while any other handle that refers to it is not yet
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closed; for example, database environment handles must not be closed
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while transactions in the environment
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have not yet been committed or aborted. Specifically, this includes the
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<a class="link" href="txn.html" title="Chapter 12. The DB_TXN Handle">DB_TXN</a>,
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<a class="link" href="logc.html" title="The DB_LOGC Handle">DB_LOGC</a> and
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<a class="link" href="memp.html" title="Chapter 8. The DB_MPOOLFILE Handle">DB_MPOOLFILE</a> handles.
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</p>
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<p>
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Where the environment was initialized with the
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<a class="link" href="envopen.html#envopen_DB_INIT_LOCK">DB_INIT_LOCK</a> flag,
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calling <code class="methodname">DB_ENV->close()</code> does not release any locks still held by the
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closing process, providing functionality for long-lived locks.
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Processes that want to have all their locks released can do so by
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issuing the appropriate <a class="xref" href="lockvec.html" title="DB_ENV->lock_vec()">DB_ENV->lock_vec()</a> call.
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</p>
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<p>
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Where the environment was initialized with the
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<a class="link" href="envopen.html#envopen_DB_INIT_MPOOL">DB_INIT_MPOOL</a> flag,
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calling <code class="methodname">DB_ENV->close()</code> implies calls to
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<a class="xref" href="mempfclose.html" title="DB_MPOOLFILE->close()">DB_MPOOLFILE->close()</a> for any
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remaining open files in the memory pool that were returned to this
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process by calls to <a class="xref" href="mempfopen.html" title="DB_MPOOLFILE->open()">DB_MPOOLFILE->open()</a>. It does
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not imply a call to <a class="xref" href="mempfsync.html" title="DB_MPOOLFILE->sync()">DB_MPOOLFILE->sync()</a> for those
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files.
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</p>
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<p>
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Where the environment was initialized with the
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<a class="link" href="envopen.html#envopen_DB_INIT_TXN">DB_INIT_TXN</a>
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flag, calling <code class="methodname">DB_ENV->close()</code> aborts any
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unresolved transactions. Applications should not depend on this
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behavior for transactions involving Berkeley DB databases; all
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such transactions should be explicitly resolved. The problem with
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depending on this semantic is that aborting an unresolved
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transaction involving database operations requires a database
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handle. Because the database handles should have been closed
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before calling <code class="methodname">DB_ENV->close()</code>, it will not
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be possible to abort the transaction, and recovery will have to be
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run on the Berkeley DB environment before further operations are
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done.
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</p>
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<p>
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Where log cursors were created using the
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<a class="xref" href="logcursor.html" title="DB_ENV->log_cursor()">DB_ENV->log_cursor()</a> method,
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calling <code class="methodname">DB_ENV->close()</code> does not imply
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closing those cursors.
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</p>
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<p>
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In multithreaded applications, only a single thread may call the
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<code class="methodname">DB_ENV->close()</code> method.
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</p>
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<p>
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After <code class="methodname">DB_ENV->close()</code> has been called,
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regardless of its return, the Berkeley DB environment handle may
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not be accessed again.
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</p>
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<p>
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The <code class="methodname">DB_ENV->close()</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="id3883557"></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="id3883657"></a>flags</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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The <span class="bold"><strong>flags</strong></span> parameter must be set to 0
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or be set to the following value:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="dbenvclose_DB_FORCESYNC"></a>
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<code class="literal">DB_FORCESYNC</code>
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</p>
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<p>
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When closing each database handle internally,
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synchronize the database. If this flag is not
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specified, the database handle is closed without
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synchronizing the database.
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</p>
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</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="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="id3884207"></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="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</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="id3884141"></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="env.html#envlist" title="Database Environments and Related Methods">Database Environments 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="envadd_data_dir.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="env.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="envcreate.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_ENV->add_data_dir() </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_env_create</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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