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216 lines
9 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_errcall()</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_encrypt.html" title="Db::set_encrypt()" />
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<link rel="next" href="dbset_errfile.html" title="Db::set_errfile()" />
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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::set_errcall()</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_encrypt.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_errfile.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="dbset_errcall"></a>Db::set_errcall()</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_cxx.h>
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void Db::set_errcall(void (*db_errcall_fcn)
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(const DbEnv *dbenv, const char *errpfx, const char *msg));</pre>
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<p>
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When an error occurs in the Berkeley DB library,
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<span>
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an exception is thrown
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</span>
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or an error return value is returned by the interface. In some cases,
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however, the <span class="bold"><strong>errno</strong></span> value may be
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insufficient to completely describe the cause of the error, especially
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during initial application debugging.
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</p>
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<p>
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The <a class="xref" href="envset_errcall.html" title="DbEnv::set_errcall()">DbEnv::set_errcall()</a> and
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<code class="methodname">Db::set_errcall()</code> methods are used to enhance the mechanism for
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reporting error messages to the application. In some cases, when an
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error occurs, Berkeley DB will call <span class="bold"><strong>db_errcall_fcn()</strong></span>
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with additional error information. It is up to the
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<span class="bold"><strong>db_errcall_fcn()</strong></span> function to display the error
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message in an appropriate manner.
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</p>
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<p>
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Setting <span class="bold"><strong>db_errcall_fcn</strong></span> to NULL
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unconfigures the callback interface.
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</p>
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<p>
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Alternatively, you can use the
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<span>
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<a class="xref" href="envset_error_stream.html" title="DbEnv::set_error_stream()">DbEnv::set_error_stream()</a>
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and
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<a class="xref" href="dbset_error_stream.html" title="Db::set_error_stream()">Db::set_error_stream()</a>
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methods to display the additional information via an output stream, or the
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</span>
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<a class="xref" href="dbset_errfile.html" title="Db::set_errfile()">Db::set_errfile()</a> or
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<a class="xref" href="envset_errfile.html" title="DbEnv::set_errfile()">Db::set_errfile()</a>
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methods to display the additional information via a C library <code class="literal">FILE *</code>.
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<span>You should not mix these approaches.</span>
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</p>
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<p>
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This error-logging enhancement does not slow performance or
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significantly increase application size, and may be run during normal
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operation as well as during application debugging.
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</p>
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<p>
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For <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handles opened
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inside of Berkeley DB environments, calling the
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<code class="methodname">Db::set_errcall()</code>
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method affects the entire environment and is equivalent to calling the
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<a class="xref" href="envset_errcall.html" title="DbEnv::set_errcall()">DbEnv::set_errcall()</a>
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method.
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</p>
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<p>
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When used on a database that was <span class="emphasis"><em>not</em></span> opened in
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an environment, the <code class="methodname">Db::set_errcall()</code>
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method configures operations performed using the specified
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<a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handle, not all operations
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performed on the underlying database.
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</p>
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<p>
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The <code class="methodname">Db::set_errcall()</code> method may be called at any time during the
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life of the application.
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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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Berkeley DB is not re-entrant. Callback functions should not attempt to make library
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calls (for example, to release locks or close open handles). Re-entering Berkeley DB is
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not guaranteed to work correctly, and the results are undefined.
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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="id3594218"></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="id3594221"></a>db_errcall_fcn</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>db_errcall_fcn</strong></span> parameter is the
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application-specified error reporting function. The function takes
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three parameters:
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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>
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<code class="literal">dbenv</code>
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</p>
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<p>
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The <span class="bold"><strong>dbenv</strong></span> parameter is the enclosing
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database environment.
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</p>
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</li>
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<li>
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<p>
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<code class="literal">errpfx</code>
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</p>
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<p>
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The <span class="bold"><strong>errpfx</strong></span> parameter is the prefix
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string (as previously set by
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<a class="xref" href="dbset_errpfx.html" title="Db::set_errpfx()">Db::set_errpfx()</a> or
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<a class="xref" href="envset_errpfx.html" title="DbEnv::set_errpfx()">DbEnv::set_errpfx()</a> ).
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</p>
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</li>
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<li>
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<p>
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<code class="literal">msg</code>
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</p>
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<p>
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The <span class="bold"><strong>msg</strong></span> parameter is the error
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message string.
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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="id3594300"></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="id3594128"></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_encrypt.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_errfile.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_encrypt() </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_errfile()</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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