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197 lines
8.3 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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DB_ENV->set_lg_bsize()</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="lsn.html" title="Chapter 7. The DB_LSN Handle" />
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<link rel="prev" href="logstat_print.html" title="DB_ENV->log_stat_print()" />
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<body>
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<div xmlns="" class="navheader">
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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->set_lg_bsize()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="logstat_print.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 7.
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The DB_LSN Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="envset_lg_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_lg_bsize"></a>DB_ENV->set_lg_bsize()</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->set_lg_bsize(DB_ENV *dbenv, u_int32_t lg_bsize); </pre>
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<p>
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Sets the size of the in-memory log buffer, in bytes.
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</p>
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<p>
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When the logging subsystem is configured for on-disk logging, the
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default size of the in-memory log buffer is approximately 32KB. Log
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information is stored in-memory until the storage space fills up or
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transaction commit forces the information to be flushed to stable
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storage. In the presence of long-running transactions or transactions
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producing large amounts of data, larger buffer sizes can increase
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throughput.
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</p>
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<p>
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When the logging subsystem is configured for in-memory logging, the
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default size of the in-memory log buffer is 1MB. Log information is
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stored in-memory until the storage space fills up or transaction abort
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or commit frees up the memory for new transactions. In the presence
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of long-running transactions or transactions producing large amounts
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of data, the buffer size must be sufficient to hold all log
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information that can accumulate during the longest running
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transaction. When choosing log buffer and file sizes for in-memory
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logs, applications should ensure the in-memory log buffer size is
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large enough that no transaction will ever span the entire buffer, and
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avoid a state where the in-memory buffer is full and no space can be
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freed because a transaction that started in the first log "file" is
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still active.
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</p>
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<p>
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The database environment's log buffer size may also be configured
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using the environment's <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file. The syntax of the entry
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in that file is a single line with the string "set_lg_bsize", one
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or more whitespace characters, and the size in bytes. Because the
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is read when the database environment is opened,
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it will silently overrule configuration done before that time.
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</p>
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<p>
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The <code class="methodname">DB_ENV->set_lg_bsize()</code> method configures a database environment,
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not only operations performed using the specified <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle.
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</p>
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<p>
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The <code class="methodname">DB_ENV->set_lg_bsize()</code> method may not be called after the
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<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method is called.
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If the database environment already exists when
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<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> is called, the
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information specified to <code class="methodname">DB_ENV->set_lg_bsize()</code> will be ignored.
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</p>
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<p>
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The <code class="methodname">DB_ENV->set_lg_bsize()</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="idp60984392"></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="idp60984240"></a>lg_bsize</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>lg_bsize</strong></span> parameter is the size of
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the in-memory log buffer, in bytes.
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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="idp60956320"></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->set_lg_bsize()</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="idp60988808"></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="idp60974424"></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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<a class="link" href="logc.html" title="The DB_LOGC Handle">DB_LOGC</a>,
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<a class="link" href="lsn.html" title="Chapter 7. The DB_LSN Handle">DB_LSN</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="idp60983528"></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="lsn.html#loglist" title="Logging Subsystem and Related Methods">Logging 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="logstat_print.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="lsn.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="envset_lg_dir.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->log_stat_print() </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->set_lg_dir()</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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