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12 KiB
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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>DbEnv::set_app_dispatch()</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 DbEnv Handle" />
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<link rel="prev" href="envset_alloc.html" title="DbEnv::set_alloc()" />
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<link rel="next" href="envset_data_dir.html" title="DbEnv::set_data_dir()" />
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</head>
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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">DbEnv::set_app_dispatch()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="envset_alloc.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5.
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The DbEnv Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="envset_data_dir.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="envset_app_dispatch"></a>DbEnv::set_app_dispatch()</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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int
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DbEnv::set_app_dispatch(int (*tx_recover)(DbEnv *dbenv,
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Dbt *log_rec, DbLsn *lsn, db_recops op));</pre>
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<p>
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Declare a function to be called during transaction abort and recovery
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to process application-specific log records.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_app_dispatch()</code> method configures operations performed
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using the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle, not all
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operations performed on the underlying database environment.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_app_dispatch()</code> method may not be called after the
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<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is
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called. If the database environment already exists when
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<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> is called, the
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information specified to <code class="methodname">DbEnv::set_app_dispatch()</code> must be
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consistent with the existing environment or corruption can occur.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_app_dispatch()</code> method returns a non-zero error value
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on failure and 0 on success.
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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="id3619626"></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="id3619712"></a>tx_recover</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>tx_recover</strong></span> parameter is the
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application's abort and recovery function. The function takes four
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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 handle.
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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">log_rec</code>
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</p>
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<p>
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The <span class="bold"><strong>log_rec</strong></span> parameter is a log
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record.
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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">lsn</code>
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</p>
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<p>
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The <span class="bold"><strong>lsn</strong></span> parameter is a log sequence
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number.
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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">op</code>
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</p>
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<p>
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The <span class="bold"><strong>op</strong></span> parameter is one of the
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following values:
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</p>
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<div class="itemizedlist">
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<ul type="circle">
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<li>
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<p><a id="set_app_dispatch_DB_TXN_BACKWARD_ROLL"></a>
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<code class="literal">DB_TXN_BACKWARD_ROLL</code>
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</p>
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<p>
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The log is being read backward to determine which transactions have
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been committed and to abort those operations that were not; undo the
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operation described by the log record.
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</p>
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</li>
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<li>
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<p><a id="set_app_dispatch_DB_TXN_FORWARD_ROLL"></a>
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<code class="literal">DB_TXN_FORWARD_ROLL</code>
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</p>
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<p>
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The log is being played forward; redo the operation described by the
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log record.
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</p>
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</li>
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<li>
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<p><a id="set_app_dispatch_DB_TXN_ABORT"></a>
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<code class="literal">DB_TXN_ABORT</code>
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</p>
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<p>
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The log is being read backward during a transaction abort; undo the
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operation described by the log record.
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</p>
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</li>
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<li>
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<p><a id="set_app_dispatch_DB_TXN_APPLY"></a>
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<code class="literal">DB_TXN_APPLY</code>
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</p>
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<p>
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The log is being applied on a replica site; redo the operation
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described by the log record.
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</p>
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</li>
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<li>
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<p><a id="set_app_dispatch_DB_TXN_PRINT"></a>
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<code class="literal">DB_TXN_PRINT</code>
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</p>
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<p>
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The log is being printed for debugging purposes; print the contents of
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this log record in the desired format.
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</p>
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</li>
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</ul>
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</div>
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<p>
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The DB_TXN_FORWARD_ROLL and DB_TXN_APPLY operations frequently imply
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the same actions, redoing changes that appear in the log record,
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although if a recovery function is to be used on a replication client
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where reads may be taking place concurrently with the processing of
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incoming messages, DB_TXN_APPLY operations should also perform
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appropriate locking. The macro DB_REDO(op) checks that the operation
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is one of DB_TXN_FORWARD_ROLL or DB_TXN_APPLY, and should be used in
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the recovery code to refer to the conditions under which operations
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should be redone. Similarly, the macro DB_UNDO(op) checks if the
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operation is one of DB_TXN_BACKWARD_ROLL or DB_TXN_ABORT.
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</p>
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</li>
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</ul>
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</div>
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<p>
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The function must return 0 on success and either <span class="bold"><strong>errno</strong></span>
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or a value outside of the Berkeley DB error name space on failure.
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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="id3620259"></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">DbEnv::set_app_dispatch()</code> <span>
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<span>
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method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
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exception, encapsulating one of the following non-zero errors, or return one
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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="id3620109"></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 <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a>
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was called; or if 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="id3620150"></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 DbEnv Handle">DbEnv</a>, <a class="link" href="txn.html" title="Chapter 13. The DbTxn Handle">DbTxn</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="id3619846"></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="txn.html#txnlist" title="Transaction Subsystem and Related Methods">Transaction Subsystem 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="envset_alloc.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="envset_data_dir.html">Next</a></td>
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<td width="40%" align="left" valign="top">DbEnv::set_alloc() </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"> DbEnv::set_data_dir()</td>
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</body>
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</html>
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