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Yasuhiro KIMURA
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557 lines
26 KiB
HTML
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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->rep_set_config()</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="rep.html" title="Chapter 10. Replication Methods" />
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<link rel="prev" href="repclockskew.html" title="DB_ENV->rep_set_clockskew()" />
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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 18.1.40</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">
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<span xmlns="http://www.w3.org/1999/xhtml">DB_ENV->rep_set_config()</span>
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</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="repclockskew.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 10.
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Replication Methods
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="repset_limit.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="repconfig"></a>
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<span>DB_ENV->rep_set_config()</span>
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</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->rep_set_config(DB_ENV *env, u_int32_t which, int onoff); </pre>
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<p>
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The <code class="methodname">DB_ENV->rep_set_config()</code> method configures the Berkeley DB
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replication subsystem.
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</p>
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<p>
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The database environment's replication subsystem may also be
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configured 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
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of the entry in that file is a single line with the string
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"rep_set_config", one or more whitespace characters, and the
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method <span class="bold"><strong>which</strong></span> 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, "rep_set_config DB_REP_CONF_NOWAIT"
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or "rep_set_config DB_REP_CONF_NOWAIT on". Because the <a href="../../programmer_reference/env_db_config.html#env_db_config.DB_CONFIG" class="olink">DB_CONFIG</a>
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file is read when the database environment is opened, it will
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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->rep_set_config()</code> method configures a database
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environment, not only operations performed using the specified
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<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->rep_set_config()</code> method may not be
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called to set in-memory replication after the environment is
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opened using the
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<a class="xref" href="envopen.html" title="DB_ENV->open()">
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<span>DB_ENV->open()</span>
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</a> method.
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This method should not be called to set preferred master mode or
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master leases after the
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<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">
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<span>DB_ENV->rep_start()</span>
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</a> or
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<a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">
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<span>DB_ENV->repmgr_start()</span>
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</a> methods
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are called. For all other <span class="bold"><strong>which</strong></span>
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parameters, this method may be called at any time during the life
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of the application.
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</p>
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<p>
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The <code class="methodname">DB_ENV->rep_set_config()</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="idm139753797515840"></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="idm139753797602528"></a>which</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>which</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="config_DB_REP_CONF_AUTOINIT"></a>
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<code class="literal">DB_REP_CONF_AUTOINIT</code>
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</p>
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<p>
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The replication master will automatically re-initialize outdated
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clients. This option is turned on by default.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REP_CONF_BULK"></a>
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<code class="literal">DB_REP_CONF_BULK</code>
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</p>
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<p>
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The replication master sends groups of records to the clients in a
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single network transfer.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REP_CONF_DELAYCLIENT"></a>
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<code class="literal">DB_REP_CONF_DELAYCLIENT</code>
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</p>
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<p>
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The client should delay synchronizing to a newly declared master.
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Clients configured in this way will remain
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unsynchronized until the application calls the
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<a class="xref" href="repsync.html" title="DB_ENV->rep_sync()">
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<span>DB_ENV->rep_sync()</span>
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</a> method.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REP_CONF_INMEM"></a>
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<code class="literal">DB_REP_CONF_INMEM</code>
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</p>
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<p>
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Store internal replication information in memory only.
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</p>
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<p>
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By default, replication creates files in the
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environment home directory to preserve some
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internal information. If this configuration flag is
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turned on, replication only stores this internal
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information in-memory and cannot keep persistent
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state across a site crash or reboot. This results
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in the following limitations:
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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>
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A master site should not reappoint itself
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master immediately after crashing or
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rebooting because the application would
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incur a slightly higher risk of client
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crashes. The former master site should
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rejoin the replication group as a client.
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The application should either hold an
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election or appoint a different site to be
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the next master.
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</p>
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</li>
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<li>
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<p>
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An application has a slightly higher risk
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that elections will fail or be unable to
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complete. Calling additional elections
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should eventually yield a winner.
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</p>
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</li>
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<li>
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<p>
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An application has a slight risk that the
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wrong site may win an election, resulting
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in the loss of some data. This is
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consistent with the general loss of data
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durability when running in-memory.
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</p>
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</li>
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<li>
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<p>
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Replication Manager applications do not
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maintain group membership
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information persistently on-disk. For more
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information, see <a href="../../programmer_reference/rep_filename.html" class="olink">Managing Replication Files</a> in the
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<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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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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This configuration flag can only be turned on
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before the environment is opened with the
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<a class="xref" href="envopen.html" title="DB_ENV->open()">
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<span>DB_ENV->open()</span>
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</a>
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method. Its value cannot be changed while the
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environment is open. All sites in the replication
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group should have the same value for this
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configuration flag.
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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">DB_REP_CONF_LEASE</code>
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</p>
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<p>
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Master leases will be used for this site.
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</p>
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<p>
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Configuring this option may result in
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<code class="literal">DB_REP_LEASE_EXPIRED</code> error returns
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from the <a class="xref" href="dbget.html" title="DB->get()">
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<span>DB->get()</span>
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</a> and
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<a class="xref" href="dbcget.html" title="DBcursor->get()">
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<span>DBcursor->get()</span>
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</a> methods
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when attempting to read entries from a database after the site's
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master lease has expired.
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</p>
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<p>
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This configuration flag may not be set after the
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<a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">
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<span>DB_ENV->repmgr_start()</span>
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</a> method or the
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<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">
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<span>DB_ENV->rep_start()</span>
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</a>
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method is called. All sites in the replication
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group should have the same value for this
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configuration flag.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REP_CONF_NOWAIT"></a>
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<code class="literal">DB_REP_CONF_NOWAIT</code>
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</p>
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<p>
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Berkeley DB method calls that would normally block while clients are
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in recovery will return errors immediately.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REPMGR_CONF_ELECTIONS"></a>
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<code class="literal">DB_REPMGR_CONF_ELECTIONS</code>
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</p>
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<p>
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Replication Manager automatically runs elections to
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choose a new master when the old master fails or
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becomes disconnected. This option is turned on
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by default. In preferred master mode, this option
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cannot be turned off.
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</p>
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<p>
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If this option is turned off, the application is
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responsible for assigning the new master
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explicitly, by calling the
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<code class="methodname">DB_ENV->repmgr_start()</code>
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method.
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</p>
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<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Caution</h3>
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<p>
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Most Replication Manager
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applications should accept the default automatic
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behavior. Allowing two sites in a replication
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group to act as master simultaneously can lead to
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loss of data.
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</p>
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</div>
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<p>
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In an application with multiple processes per
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database environment, only the replication
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process may change this configuration setting.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REPMGR_CONF_FORWARD_WRITES"></a>
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<code class="literal">DB_REPMGR_CONF_FORWARD_WRITES</code>
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</p>
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<p>
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By default, write operations cannot be performed on a
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replication client site. This option enables forwarding of
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simple client put and delete operations to the master site
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for processing. These operations must use an implicit NULL
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transaction ID to be forwarded. Any other write
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operation that specifies a non-NULL transaction or uses a cursor
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<span>returns an error.</span>
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This option is turned off by default.
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</p>
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<p>
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The master must have an open database handle for the database
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on which a forwarded write operation is being performed.
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All sites in the replication group should have the same value
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for this configuration option.
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(See the <a href="../../programmer_reference/comm_repsites.html#conf_writeforw" class="olink">Configuring for Write Forwarding</a>
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section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.)
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</p>
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</li>
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<li>
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<p><a id="config_DB_REPMGR_CONF_PREFMAS_CLIENT"></a>
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<code class="literal">DB_REPMGR_CONF_PREFMAS_CLIENT</code>
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</p>
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<p>
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This is the client site in a two-site
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replication group running in preferred master
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mode. This site automatically takes over as
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temporary master when the preferred master
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site is unavailable. Transactions committed
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on this site when it is operating as the
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temporary master may be rolled back if they
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conflict with preferred master transactions.
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(See the
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<a href="../../programmer_reference/rep_twosite.html#twosite_prefmas" class="olink">
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Preferred master mode </a>
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section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>
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for more information.) This configuration flag may
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not be set after the <a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">
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<span>DB_ENV->repmgr_start()</span>
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</a> method is called.
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</p>
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<p>
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The other site in the replication group should
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be specified as the preferred master site using the
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<code class="literal">DB_REPMGR_CONF_PREFMAS_MASTER</code>
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configuration flag.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REPMGR_CONF_PREFMAS_MASTER"></a>
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<code class="literal">DB_REPMGR_CONF_PREFMAS_MASTER</code>
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</p>
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<p>
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This is the preferred master site in a two-site
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replication group running in preferred master
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mode. This site functions as the master
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whenever its availability permits.
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When this site returns to the replication
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group after having been unavailable, it
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synchronizes with the temporary master and
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then automatically takes over as master.
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Transactions committed on this site will
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not be rolled back. (See the
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<a href="../../programmer_reference/rep_twosite.html#twosite_prefmas" class="olink">
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Preferred master mode </a>
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section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>
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for more information.) This configuration flag may not
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be set after the <a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">
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<span>DB_ENV->repmgr_start()</span>
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</a> method is called.
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</p>
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<p>
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The other site in the replication group should
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be specified as the preferred master client site
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using the
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<code class="literal">DB_REPMGR_CONF_PREFMAS_CLIENT</code>
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configuration flag.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REPMGR_CONF_2SITE_STRICT"></a>
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<code class="literal">DB_REPMGR_CONF_2SITE_STRICT</code>
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</p>
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<p>
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Replication Manager observes the strict "majority" rule in managing
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elections, even in a replication group with only two
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sites. This means the client
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in a two-site replication group will be unable to take
|
||
over as master if the
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original master fails or becomes disconnected. (See the
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<a href="../../programmer_reference/rep_twosite.html" class="olink">
|
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Special considerations for two-site replication groups
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</a>
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section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.)
|
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Both sites in the replication group should have the same value for this
|
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configuration flag. This option is turned on by
|
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default. In preferred master mode, this option cannot
|
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be turned off.
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</p>
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</li>
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<li>
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<p><a id="config_DB_REPMGR_CONF_ENABLE_EPOLL"></a>
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<code class="literal">DB_REPMGR_CONF_ENABLE_EPOLL</code>
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</p>
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<p>
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Epoll will be used for network input/output event notification for this site.
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Epoll should be used on Linux if the number of sites in the replication group is
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more than 1000.
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</p>
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<p>
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Note that, Epoll is available only on a Linux environment,
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and if you try to enable this flag on other platforms, it would result
|
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in error 3727 - "DB_ENV->rep_set_config: cannot use EPOLL on
|
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this system. OS support not available for epoll()".
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</p>
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</li>
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<li>
|
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<p><a id="config_DB_REPMGR_CONF_DISABLE_POLL"></a>
|
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<code class="literal">DB_REPMGR_CONF_DISABLE_POLL</code>
|
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</p>
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<p>
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Poll will not be used for network input/output event notification for this site.
|
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</p>
|
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<p>
|
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If the system call poll() is not available on the target platform, and you try
|
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to set this flag, it would result in error 3728 - "DB_ENV->rep_set_config: POLL
|
||
support not available on this system. Ignoring this flag".
|
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</p>
|
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</li>
|
||
<li>
|
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<p><a id="config_DB_REPMGR_CONF_DISABLE_SSL"></a>
|
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<code class="literal">DB_REPMGR_CONF_DISABLE_SSL</code>
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</p>
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<p>
|
||
Secure Sockets Layer (SSL) will not be used for securing messages for the
|
||
replication manager on this replication site.
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="sect3" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h4 class="title"><a id="idm139753797489296"></a>onoff</h4>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
If the <span class="bold"><strong>onoff</strong></span> parameter
|
||
is zero, the configuration flag is turned off.
|
||
Otherwise, it is turned on. Most configuration flags are
|
||
turned off by default, exceptions are noted above.
|
||
</p>
|
||
</div>
|
||
</div>
|
||
<div class="sect2" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h3 class="title"><a id="idm139753797453040"></a>Errors</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
The <code class="methodname">DB_ENV->rep_set_config()</code> <span>
|
||
<span>
|
||
method may fail and 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="idm139753797449568"></a>EINVAL</h4>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
If setting in-memory replication after the database environment is already
|
||
opened; if setting preferred master or master leases
|
||
after replication is started; if setting a Replication
|
||
Manager configuration flag for a Base API application;
|
||
or if 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="idm139753797456368"></a>Class</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
|
||
</p>
|
||
</div>
|
||
<div class="sect2" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h3 class="title"><a id="idm139753797483696"></a>See Also</h3>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
<a class="xref" href="rep.html#replist" title="Replication and Related Methods">Replication 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="repclockskew.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="rep.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="repset_limit.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">
|
||
<span>DB_ENV->rep_set_clockskew()</span>
|
||
|
||
</td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top">
|
||
<span>DB_ENV->rep_set_limit()</span>
|
||
|
||
</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|