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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DB_ENV->failchk()</title>
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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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="enverr.html" title="DB_ENV->err()" />
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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_ENV->failchk()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="enverr.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="envfileid_reset.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="envfailchk"></a>DB_ENV->failchk()</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->failchk(DB_ENV *dbenv, u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB_ENV->failchk()</code> method checks for threads of control (either a
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true thread or a process) that have exited while manipulating Berkeley
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DB library data structures, while holding a logical database lock, or
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with an unresolved transaction (that is, a transaction that was never
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aborted or committed). For more information, see
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<a href="../../programmer_reference/cam_app.html" class="olink">Architecting Data Store and
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Concurrent Data Store applications</a>, and
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<a href="../../programmer_reference/transapp_app.html" class="olink">Architecting Transactional
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Data Store applications</a>, both in the
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<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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<p>
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The <code class="methodname">DB_ENV->failchk()</code> method is
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used in conjunction with the
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<a class="xref" href="envset_thread_count.html" title="DB_ENV->set_thread_count()">DB_ENV->set_thread_count()</a>,
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<a class="xref" href="envset_isalive.html" title="DB_ENV->set_isalive()">DB_ENV->set_isalive()</a> and
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<a class="xref" href="envset_thread_id.html" title="DB_ENV->set_thread_id()">DB_ENV->set_thread_id()</a>
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methods. Before calling the <code class="methodname">failchk()</code>method, applications must:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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Configure their database using the
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<a class="xref" href="envset_thread_count.html" title="DB_ENV->set_thread_count()">DB_ENV->set_thread_count()</a>
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method.
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</p>
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</li>
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<li>
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<p>
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Establish an <code class="literal">is_alive()</code> function and
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invoke
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<a class="xref" href="envset_isalive.html" title="DB_ENV->set_isalive()">DB_ENV->set_isalive()</a>
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with that function as the <code class="literal">is_alive</code> parameter.
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</p>
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</li>
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<li>
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<p>
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Establish a <code class="literal">thread_id</code> function and
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invoke
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<a class="xref" href="envset_thread_id.html" title="DB_ENV->set_thread_id()">DB_ENV->set_thread_id()</a>
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with that function as the <code class="literal">thread_id</code>
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parameter.
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</p>
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</li>
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</ol>
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</div>
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<p>
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If any of these methods are omitted, a program may be unable to
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allocate a thread control block. This is true of the standalone
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Berkeley DB utility programs. To avoid problems when using the
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standalone Berkeley DB utility programs with environments
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configured for failure checking, incorporate the utility's
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functionality directly in the application, or call the
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<code class="methodname">DB_ENV->failchk()</code> method along with its
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associated methods before running the utility.
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</p>
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<p>
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If <code class="methodname">DB_ENV->failchk()</code> determines a thread of control exited while
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holding database read locks, it will release those locks. If
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<code class="methodname">DB_ENV->failchk()</code> determines a thread of control exited with an
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unresolved transaction, the transaction will be aborted. In either of
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these cases, <code class="methodname">DB_ENV->failchk()</code> will return 0 and the application may
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continue to use the database environment.
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</p>
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<p>
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In either of these cases, the <code class="methodname">DB_ENV->failchk()</code> method will also
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report the process and thread IDs associated with any released locks
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or aborted transactions. The information is printed to a specified
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output channel (see the
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<a class="xref" href="envset_msgfile.html" title="DB_ENV->set_msgfile()">DB_ENV->set_msgfile()</a>
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method for more information), or passed to an application callback
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function (see the
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<a class="xref" href="envset_msgcall.html" title="DB_ENV->set_msgcall()">DB_ENV->set_msgcall()</a>
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method for more information).
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</p>
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<p>
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If <code class="methodname">DB_ENV->failchk()</code> determines a thread of control has exited such
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that database environment recovery is required, it will return
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<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>.
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In this case, the application should not continue to use the database
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environment. For a further description as to the actions the
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application should take when this failure occurs, see
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<a href="../../programmer_reference/cam_fail.html" class="olink">Handling failure in Data Store and
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Concurrent Data Store applications</a>, and
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<a href="../../programmer_reference/transapp_fail.html" class="olink">Handling failure in Transactional Data
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Store applications</a>, both in the
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<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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<p>
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In multiprocess applications, it is recommended that the <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle
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used to invoke the <code class="methodname">DB_ENV->failchk()</code> method not be shared and therefore
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not <span class="emphasis"><em>free-threaded</em></span>.
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</p>
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<p>
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The <code class="methodname">DB_ENV->failchk()</code> method may not be called by the
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application before the <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a>
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method is called.
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</p>
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<p>
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The <code class="methodname">DB_ENV->failchk()</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="idp59319432"></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="idp59391152"></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 is currently
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unused, and must be set to 0.
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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="idp59396112"></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_ENV->failchk()</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="idp59321376"></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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An invalid flag value or 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="idp59396760"></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="idp59390720"></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="enverr.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="envfileid_reset.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->err() </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->fileid_reset()</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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