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658 lines
36 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_flags()</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="env.html" title="Chapter 5. The DbEnv Handle" />
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<link rel="prev" href="envset_feedback.html" title="DbEnv::set_feedback()" />
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<link rel="next" href="envset_intermediate_dir_mode.html" title="DbEnv::set_intermediate_dir_mode()" />
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</head>
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<body>
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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_flags()</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_feedback.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_intermediate_dir_mode.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_flags"></a>DbEnv::set_flags()</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_flags(u_int32_t flags, int onoff); </pre>
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<p>
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Configure a database environment.
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</p>
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<p>
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The database environment's flag values 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_flags", one or
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more whitespace characters, and the method flag parameter as a
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string, and optionally one or more whitespace characters, and the
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string "on" or "off". If the optional string is omitted, the
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default is "on"; for example, "set_flags DB_TXN_NOSYNC" or
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"set_flags DB_TXN_NOSYNC on". Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file is read
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when the database environment is opened, it will silently overrule
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configuration done before that time.
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</p>
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<p>
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The <code class="methodname">DbEnv::set_flags()</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="id3623265"></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="id3623247"></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 by
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bitwise inclusively <span class="bold"><strong>OR</strong></span>'ing together
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one or more 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="envset_flags_DB_AUTO_COMMIT"></a>
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<code class="literal">DB_AUTO_COMMIT</code>
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</p>
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<p>
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If set, <a class="link" href="db.html" title="Chapter 2. The Db Handle">Db</a> handle
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operations for which no explicit transaction handle was specified, and
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which modify databases in the database environment, will be
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automatically enclosed within a transaction.
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</p>
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<p>
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Calling <code class="methodname">DbEnv::set_flags()</code> with this flag only affects the specified
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle (and any other
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Berkeley DB handles opened within the scope of that handle). For
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consistent behavior across the environment, all
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in the
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environment must either set this flag
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or the flag should be specified in the
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
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</p>
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<p>
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This flag may be used to configure Berkeley DB at any time during the life
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of the application.
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</p>
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</li>
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<li>
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<p><a id="set_flags_DB_CDB_ALLDB"></a>
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<code class="literal">DB_CDB_ALLDB</code>
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</p>
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<p>
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If set, Berkeley DB Concurrent Data Store applications will perform
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locking on an environment-wide basis rather than on a per-database
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basis.
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</p>
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<p>
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Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_CDB_ALLDB flag only affects
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the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
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handle (and any other Berkeley DB handles opened within the scope of
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that handle). For consistent behavior across the environment, all
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in
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the environment must either set the DB_CDB_ALLDB flag or the flag
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should be specified in the
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
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</p>
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<p>
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The DB_CDB_ALLDB flag may be used to configure Berkeley DB only before
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the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method
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is called.
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</p>
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</li>
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<li>
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<p><a id="set_flags_DB_DIRECT_DB"></a>
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<code class="literal">DB_DIRECT_DB</code>
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</p>
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<p>
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Turn off system buffering of Berkeley DB database files to avoid
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double caching.
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</p>
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<p>
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Calling <code class="methodname">DbEnv::set_flags()</code> with
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the DB_DIRECT_DB flag only affects the specified
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle (and any other
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Berkeley DB handles opened within the scope of that
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handle). For consistent behavior across the environment,
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all <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened
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in the environment must either set the DB_DIRECT_DB flag
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or the flag should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
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configuration file.
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</p>
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<p>
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The DB_DIRECT_DB flag may be used to configure Berkeley DB at any time
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during the life of the application.
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</p>
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</li>
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<li>
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<p><a id="set_flags_DB_HOTBACKUP_IN_PROGRESS"></a>
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<code class="literal">DB_HOTBACKUP_IN_PROGRESS</code>
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</p>
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<p>
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Set this flag prior to creating a
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hot backup of a database environment.
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If a transaction with the bulk
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insert optimization enabled (with the
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<a class="xref" href="txnbegin.html#txnbegin_DB_TXN_BULK">
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<code class="literal">DB_TXN_BULK</code>
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</a> flag) is in progress,
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setting the <code class="literal">DB_HOTBACKUP_IN_PROGRESS</code> flag
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forces a checkpoint in the environment.
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After
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this flag is set in the environment, the bulk insert
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optimization is disabled, until the flag is reset.
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Using this protocol allows a hot backup procedure to
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make a consistent copy of the database even when
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bulk transactions are ongoing. For more information, see the
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section on Hot Backup in the <span class="emphasis"><em>Getting Started
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With Transaction Processing Guide</em></span> and the description of the
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<a class="xref" href="txnbegin.html#txnbegin_DB_TXN_BULK">
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<code class="literal">DB_TXN_BULK</code>
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</a> flag in the
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<a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a> method.
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</p>
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<p>
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The <a class="xref" href="db_hotbackup.html" title="db_hotbackup">db_hotbackup</a>
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utility implements the protocol described above.
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</p>
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</li>
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<li>
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<p><a id="set_flags_DB_DSYNC_DB"></a>
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<code class="literal">DB_DSYNC_DB</code>
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</p>
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<p>
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Configure Berkeley DB to flush database writes to the backing disk
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before returning from the write system call, rather than flushing
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database writes explicitly in a separate system call, as necessary.
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This is only available on some systems (for example, systems
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supporting the IEEE/ANSI Std 1003.1 (POSIX) standard O_DSYNC flag, or
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systems supporting the Windows FILE_FLAG_WRITE_THROUGH flag). This
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flag may result in inaccurate file modification times and other
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file-level information for Berkeley DB database files. This flag will
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almost certainly result in a performance decrease on most systems.
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This flag is only applicable to certain filesysystems (for example, the
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Veritas VxFS filesystem), where the filesystem's support for trickling
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writes back to stable storage behaves badly (or more likely, has been
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misconfigured).
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</p>
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<p>
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Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_DSYNC_DB flag only affects
|
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the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
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|
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handle (and any other Berkeley DB handles opened within the scope of
|
|||
|
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that handle). For consistent behavior across the environment, all
|
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|
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<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in
|
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|
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the environment must either set the DB_DSYNC_DB flag or the flag
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should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
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</p>
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<p>
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The DB_DSYNC_DB flag may be used to configure Berkeley DB at any time
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during the life of the application.
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</p>
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</li>
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<li>
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<p><a id="set_flags_DB_MULTIVERSION"></a>
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<code class="literal">DB_MULTIVERSION</code>
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</p>
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<p>
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If set, all databases in the environment will be opened as if
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DB_MULTIVERSION is passed to the <a class="xref" href="dbopen.html" title="Db::open()">Db::open()</a>
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method. This flag will be ignored for queue databases for which DB_MULTIVERSION is not
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supported.
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</p>
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<p>
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Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_MULTIVERSION flag only
|
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affects the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle (and any other
|
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|
|
Berkeley DB handles opened within the scope of that handle). For
|
|||
|
|
consistent behavior across the environment, all <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
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handles opened in the environment must either set the DB_MULTIVERSION flag or the flag
|
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|
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should be specified in the
|
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|
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<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
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|
|
</p>
|
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<p>
|
|||
|
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The DB_MULTIVERSION flag may be used to configure Berkeley DB at any
|
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|
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time during the life of the application.
|
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</p>
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</li>
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<li>
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<p><a id="set_flags_DB_NOLOCKING"></a>
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<code class="literal">DB_NOLOCKING</code>
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</p>
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<p>
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If set, Berkeley DB will grant all requested mutual exclusion mutexes
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and database locks without regard for their actual availability. This
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functionality should never be used for purposes other than debugging.
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</p>
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<p>
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Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_NOLOCKING flag only affects
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|
the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
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|
|
handle (and any other Berkeley DB handles opened within the scope of
|
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|
|
that handle).
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|
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</p>
|
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|
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<p>
|
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|
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The DB_NOLOCKING flag may be used to configure Berkeley DB at any time
|
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|
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during the life of the application.
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|
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</p>
|
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|
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</li>
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<li>
|
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<p><a id="set_flags_DB_NOMMAP"></a>
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<code class="literal">DB_NOMMAP</code>
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|
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</p>
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<p>
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|
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If set, Berkeley DB will copy read-only database files into the local
|
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|
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cache instead of potentially mapping them into process memory (see the
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|
|
description of the <a class="xref" href="envset_mp_mmapsize.html" title="DbEnv::set_mp_mmapsize()">DbEnv::set_mp_mmapsize()</a>
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|
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method for further information).
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|
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</p>
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|
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<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_NOMMAP flag only affects the
|
|||
|
|
specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle
|
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|
|
(and any other Berkeley DB handles opened within the scope of that
|
|||
|
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handle). For consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in the
|
|||
|
|
environment must either set the DB_NOMMAP flag or the flag should be
|
|||
|
|
specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_NOMMAP flag may be used to configure Berkeley DB at any time
|
|||
|
|
during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_NOPANIC"></a>
|
|||
|
|
<code class="literal">DB_NOPANIC</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, Berkeley DB will ignore any panic state in the database
|
|||
|
|
environment. (Database environments in a panic state normally refuse
|
|||
|
|
all attempts to call Berkeley DB functions, returning
|
|||
|
|
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>.)
|
|||
|
|
This functionality should never be used for purposes other than
|
|||
|
|
debugging.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_NOPANIC flag only affects the
|
|||
|
|
specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle
|
|||
|
|
(and any other Berkeley DB handles opened within the scope of that
|
|||
|
|
handle).
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_NOPANIC flag may be used to configure Berkeley DB at any time
|
|||
|
|
during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_OVERWRITE"></a>
|
|||
|
|
<code class="literal">DB_OVERWRITE</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Overwrite files stored in encrypted formats before deleting them.
|
|||
|
|
Berkeley DB overwrites files using alternating 0xff, 0x00 and 0xff
|
|||
|
|
byte patterns. For file overwriting to be effective, the underlying
|
|||
|
|
file must be stored on a fixed-block filesystem. Systems with
|
|||
|
|
journaling or logging filesystems will require operating system
|
|||
|
|
support and probably modification of the Berkeley DB sources.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_OVERWRITE flag only affects
|
|||
|
|
the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of
|
|||
|
|
that handle).
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_OVERWRITE flag may be used to configure Berkeley DB at any time
|
|||
|
|
during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_PANIC_ENVIRONMENT"></a>
|
|||
|
|
<code class="literal">DB_PANIC_ENVIRONMENT</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, Berkeley DB will set the panic state for the database
|
|||
|
|
environment. (Database environments in a panic state normally refuse
|
|||
|
|
all attempts to call Berkeley DB functions, returning
|
|||
|
|
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_RUNRECOVERY" class="olink">DB_RUNRECOVERY</a>.)
|
|||
|
|
This flag may not be specified using the environment's
|
|||
|
|
<a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_PANIC_ENVIRONMENT flag
|
|||
|
|
affects the database environment, including all threads of control
|
|||
|
|
accessing the database environment.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_PANIC_ENVIRONMENT flag may be used to configure Berkeley DB
|
|||
|
|
only after the <a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method is called.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_REGION_INIT"></a>
|
|||
|
|
<code class="literal">DB_REGION_INIT</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
In some applications, the expense of page-faulting the underlying
|
|||
|
|
shared memory regions can affect performance. (For example, if the
|
|||
|
|
page-fault occurs while holding a lock, other lock requests can
|
|||
|
|
convoy, and overall throughput may decrease.) If set, Berkeley DB
|
|||
|
|
will page-fault shared regions into memory when initially creating or
|
|||
|
|
joining a Berkeley DB environment. In addition, Berkeley DB will
|
|||
|
|
write the shared regions when creating an environment, forcing the
|
|||
|
|
underlying virtual memory and filesystems to instantiate both the
|
|||
|
|
necessary memory and the necessary disk space. This can also avoid
|
|||
|
|
out-of-disk space failures later on.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_REGION_INIT flag only affects
|
|||
|
|
the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of
|
|||
|
|
that handle). For consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in
|
|||
|
|
the environment must either set the DB_REGION_INIT flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_REGION_INIT flag may be used to configure Berkeley DB at any
|
|||
|
|
time during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="envset_flags_DB_TIME_NOTGRANTED"></a>
|
|||
|
|
<code class="literal">DB_TIME_NOTGRANTED</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, database calls timing out based on lock or transaction timeout
|
|||
|
|
values will return
|
|||
|
|
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_LOCK_NOTGRANTED" class="olink">DB_LOCK_NOTGRANTED</a>
|
|||
|
|
instead of
|
|||
|
|
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_LOCK_DEADLOCK" class="olink">DB_LOCK_DEADLOCK</a>.
|
|||
|
|
This allows applications to distinguish between operations which have
|
|||
|
|
deadlocked and operations which have exceeded their time limits.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_TIME_NOTGRANTED flag only
|
|||
|
|
affects the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle (and any other
|
|||
|
|
Berkeley DB handles opened within the scope of that handle). For
|
|||
|
|
consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in the
|
|||
|
|
environment must either set the DB_TIME_NOTGRANTED flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The <code class="literal">DB_TIME_NOTGRANTED</code> flag may be used to configure Berkeley DB at
|
|||
|
|
any time during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Note that the <a class="xref" href="lockget.html" title="DbEnv::lock_get()">DbEnv::lock_get()</a>
|
|||
|
|
and <a class="xref" href="lockvec.html" title="DbEnv::lock_vec()">DbEnv::lock_vec()</a>
|
|||
|
|
methods are unaffected by this flag.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="envset_flags_DB_TXN_NOSYNC"></a>
|
|||
|
|
<code class="literal">DB_TXN_NOSYNC</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, Berkeley DB will not write or synchronously flush the log on
|
|||
|
|
transaction commit. This means that transactions exhibit the ACI
|
|||
|
|
(atomicity, consistency, and isolation) properties, but not D
|
|||
|
|
(durability); that is, database integrity will be maintained, but if
|
|||
|
|
the application or system fails, it is possible some number of the
|
|||
|
|
most recently committed transactions may be undone during recovery.
|
|||
|
|
The number of transactions at risk is governed by how many log updates
|
|||
|
|
can fit into the log buffer, how often the operating system flushes
|
|||
|
|
dirty buffers to disk, and how often the log is checkpointed.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_TXN_NOSYNC flag only affects
|
|||
|
|
the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of
|
|||
|
|
that handle). For consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in
|
|||
|
|
the environment must either set the DB_TXN_NOSYNC flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_TXN_NOSYNC flag may be used to configure Berkeley DB at any
|
|||
|
|
time during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_TXN_NOWAIT"></a>
|
|||
|
|
<code class="literal">DB_TXN_NOWAIT</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set and a lock is unavailable for any Berkeley DB operation
|
|||
|
|
performed in the context of a transaction, cause the operation to
|
|||
|
|
return
|
|||
|
|
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_LOCK_DEADLOCK" class="olink">DB_LOCK_DEADLOCK</a>
|
|||
|
|
(or
|
|||
|
|
<a href="../../programmer_reference/program_errorret.html#program_errorret.DB_LOCK_NOTGRANTED" class="olink">DB_LOCK_NOTGRANTED</a>
|
|||
|
|
if configured using the DB_TIME_NOTGRANTED flag).
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_TXN_NOWAIT flag only affects
|
|||
|
|
the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of
|
|||
|
|
that handle). For consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in
|
|||
|
|
the environment must either set the DB_TXN_NOWAIT flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_TXN_NOWAIT flag may be used to configure Berkeley DB at any
|
|||
|
|
time during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_TXN_SNAPSHOT"></a>
|
|||
|
|
<code class="literal">DB_TXN_SNAPSHOT</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, all transactions in the environment will be started as if
|
|||
|
|
DB_TXN_SNAPSHOT were passed to the
|
|||
|
|
<a class="xref" href="txnbegin.html" title="DbEnv::txn_begin()">DbEnv::txn_begin()</a> method, and all
|
|||
|
|
non-transactional cursors will be opened as if DB_TXN_SNAPSHOT were
|
|||
|
|
passed to the <a class="xref" href="dbcursor.html" title="Db::cursor()">Db::cursor()</a> method.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_TXN_SNAPSHOT flag only
|
|||
|
|
affects the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of that handle). For
|
|||
|
|
consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in the
|
|||
|
|
environment must either set the DB_TXN_SNAPSHOT flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_TXN_SNAPSHOT flag may be used to configure Berkeley DB at any
|
|||
|
|
time during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_TXN_WRITE_NOSYNC"></a>
|
|||
|
|
<code class="literal">DB_TXN_WRITE_NOSYNC</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, Berkeley DB will write, but will not synchronously flush, the
|
|||
|
|
log on transaction commit. This means that transactions exhibit the
|
|||
|
|
ACI (atomicity, consistency, and isolation) properties, but not D
|
|||
|
|
(durability); that is, database integrity will be maintained, but if
|
|||
|
|
the system fails, it is possible some number of the most recently
|
|||
|
|
committed transactions may be undone during recovery. The number of
|
|||
|
|
transactions at risk is governed by how often the system flushes dirty
|
|||
|
|
buffers to disk and how often the log is checkpointed.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_TXN_WRITE_NOSYNC flag only
|
|||
|
|
affects the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of that handle). For
|
|||
|
|
consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in the
|
|||
|
|
environment must either set the DB_TXN_WRITE_NOSYNC flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_TXN_WRITE_NOSYNC flag may be used to configure Berkeley DB at
|
|||
|
|
any time during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p><a id="set_flags_DB_YIELDCPU"></a>
|
|||
|
|
<code class="literal">DB_YIELDCPU</code>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
If set, Berkeley DB will yield the processor immediately after each
|
|||
|
|
page or mutex acquisition. This functionality should never be used
|
|||
|
|
for purposes other than stress testing.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Calling <code class="methodname">DbEnv::set_flags()</code> with the DB_YIELDCPU flag only affects
|
|||
|
|
the specified <a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
handle (and any other Berkeley DB handles opened within the scope of
|
|||
|
|
that handle). For consistent behavior across the environment, all
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handles opened in
|
|||
|
|
the environment must either set the DB_YIELDCPU flag or the flag
|
|||
|
|
should be specified in the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a> configuration file.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The DB_YIELDCPU flag may be used to configure Berkeley DB at any time
|
|||
|
|
during the life of the application.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
</ul>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="sect3" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h4 class="title"><a id="id3623257"></a>onoff</h4>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
If the <span class="bold"><strong>onoff</strong></span> parameter is zero, the
|
|||
|
|
specified flags are cleared; otherwise they are set.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="id3622764"></a>Errors</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
The <code class="methodname">DbEnv::set_flags()</code> <span>
|
|||
|
|
|
|||
|
|
<span>
|
|||
|
|
method may fail and throw a <a class="link" href="dbexception.html" title="Chapter 6. The DbException Class">DbException</a>
|
|||
|
|
exception, encapsulating one of the following non-zero errors, or return one
|
|||
|
|
of the following non-zero errors:
|
|||
|
|
</span>
|
|||
|
|
</span>
|
|||
|
|
</p>
|
|||
|
|
<div class="sect3" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h4 class="title"><a id="id3623825"></a>EINVAL</h4>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
An invalid flag value or parameter was specified.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="id3623598"></a>Class</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a>
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
<div class="sect2" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h3 class="title"><a id="id3622920"></a>See Also</h3>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<div class="navfooter">
|
|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="envset_feedback.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="env.html">Up</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="envset_intermediate_dir_mode.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top">DbEnv::set_feedback() </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top"> DbEnv::set_intermediate_dir_mode()</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|