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291 lines
13 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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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>DbLogc::get()</title>
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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 8. The DbLsn Handle" />
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<link rel="prev" href="logcclose.html" title="DbLogc::close()" />
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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">DbLogc::get()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="logcclose.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 8.
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The DbLsn Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="logcompare.html">Next</a></td>
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</table>
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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="logcget"></a>DbLogc::get()</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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DbLogc::get(DbLsn *lsn, Dbt *data, u_int32_t flags);</pre>
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<p>
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The <code class="methodname">DbLogc::get()</code> method returns records from the log.
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</p>
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<p>
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Unless otherwise specified, the <code class="methodname">DbLogc::get()</code> <span>
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<span>
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method either returns a non-zero error value or throws an
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exception that encapsulates a non-zero error value on
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failure, and returns 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="id3642249"></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="id3642238"></a>lsn</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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When the <span class="bold"><strong>flag</strong></span> parameter is set to
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DB_CURRENT, DB_FIRST, DB_LAST, DB_NEXT or DB_PREV, the <span class="bold"><strong>lsn</strong></span> parameter is overwritten with the
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<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a> value of the record
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retrieved. When <span class="bold"><strong>flag</strong></span> is set to
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DB_SET, the <span class="bold"><strong>lsn</strong></span> parameter is the
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<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a> value of the
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record to be retrieved.
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</p>
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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="id3642187"></a>data</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 data field of the <span class="bold"><strong>data</strong></span> structure
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is set to the record retrieved, and the size field indicates the
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number of bytes in the record. See
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> for a description of other
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fields in the <span class="bold"><strong>data</strong></span> structure. The
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<a class="link" href="dbt.html#dbt_DB_DBT_MALLOC">DB_DBT_MALLOC</a>,
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<a class="link" href="dbt.html#dbt_DB_DBT_REALLOC">DB_DBT_REALLOC</a>
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and <a class="link" href="dbt.html#dbt_DB_DBT_USERMEM">DB_DBT_USERMEM</a>
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flags may be specified for any
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<a class="link" href="dbt.html" title="Chapter 4. The Dbt Handle">Dbt</a> used for data retrieval.
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</p>
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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="id3641521"></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
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one of the following values:
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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="get_DB_CURRENT"></a>
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<code class="literal">DB_CURRENT</code>
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</p>
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<p>
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Return the log record to which the log currently refers.
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</p>
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</li>
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<li>
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<p><a id="get_DB_FIRST"></a>
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<code class="literal">DB_FIRST</code>
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</p>
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<p>
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The first record from any of the log files found in the log directory
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is returned in the <span class="bold"><strong>data</strong></span> parameter.
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The <span class="bold"><strong>lsn</strong></span> parameter is overwritten with
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the <a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a> of the record
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returned.
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</p>
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<p>
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The <code class="methodname">DbLogc::get()</code> method will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a> if
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DB_FIRST is set and the log is empty.
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</p>
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</li>
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<li>
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<p><a id="get_DB_LAST"></a>
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<code class="literal">DB_LAST</code>
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</p>
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<p>
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The last record in the log is returned in the <span class="bold"><strong>data</strong></span> parameter. The <span class="bold"><strong>lsn</strong></span> parameter is overwritten with the
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<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a> of the record returned.
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</p>
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<p>
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The <code class="methodname">DbLogc::get()</code> method will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a> if
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DB_LAST is set and the log is empty.
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</p>
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</li>
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<li>
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<p><a id="get_DB_NEXT"></a>
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<code class="literal">DB_NEXT</code>
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</p>
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<p>
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The current log position is advanced to the next record in the log,
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and that record is returned in the <span class="bold"><strong>data</strong></span> parameter. The <span class="bold"><strong>lsn</strong></span> parameter is overwritten with the
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<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a> of the record returned.
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</p>
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<p>
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If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET,
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DB_NEXT, or DB_PREV, <code class="methodname">DbLogc::get()</code> will return the first record in
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the log.
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</p>
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<p>
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The <code class="methodname">DbLogc::get()</code> method will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a> if
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DB_NEXT is set and the last log record has already been returned or
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the log is empty.
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</p>
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</li>
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<li>
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<p><a id="get_DB_PREV"></a>
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<code class="literal">DB_PREV</code>
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</p>
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<p>
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The current log position is advanced to the previous record in the
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log, and that record is returned in the <span class="bold"><strong>data</strong></span> parameter. The <span class="bold"><strong>lsn</strong></span> parameter is overwritten with the
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<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</a> of the record returned.
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</p>
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<p>
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If the cursor has not been initialized via DB_FIRST, DB_LAST, DB_SET,
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DB_NEXT, or DB_PREV, <code class="methodname">DbLogc::get()</code> will return the last record in
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the log.
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</p>
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<p>
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The <code class="methodname">DbLogc::get()</code> method will return <a href="../../programmer_reference/program_errorret.html#program_errorret.DB_NOTFOUND" class="olink">DB_NOTFOUND</a> if
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DB_PREV is set and the first log record has already been returned or
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the log is empty.
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</p>
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</li>
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<li>
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<p><a id="get_DB_SET"></a>
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<code class="literal">DB_SET</code>
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</p>
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<p>
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Retrieve the record specified by the <span class="bold"><strong>lsn</strong></span> parameter.
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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="id3641523"></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">DbLogc::get()</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="id3642615"></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 DB_CURRENT flag was set and the log cursor has not yet been
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initialized; the DB_CURRENT, DB_NEXT, or DB_PREV flags were set and
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the log was opened with the DB_THREAD flag set; the DB_SET flag was
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set and the specified log sequence number does not appear in the log;
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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="id3642287"></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>,
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<a class="link" href="logc.html" title="The DbLogc Handle">DbLogc</a>,
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<a class="link" href="lsn.html" title="Chapter 8. The DbLsn Handle">DbLsn</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="id3642508"></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="logcclose.html">Prev</a> </td>
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<td width="20%" align="center">
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|||
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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="logcompare.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">DbLogc::close() </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::log_compare()</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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