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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="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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<p>Library Version 11.2.5.2</p>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">DB_ENV->rep_set_config()</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 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>DB_ENV->rep_set_config()</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()">DB_ENV->open()</a> method.
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This method may also not be called to set master leases after the
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<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</a> or
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<a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">DB_ENV->repmgr_start()</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="id3928480"></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="id3927701"></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()">DB_ENV->rep_sync()</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 environment home directory
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to preserve some internal information. If this configuration flag is turned
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on, replication only stores this internal information in-memory and cannot
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keep persistent state across a site crash or reboot. This results in the
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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 master
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immediately after crashing or rebooting because the application would incur a
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slightly higher risk of client crashes. The former master site should rejoin
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the replication group as a client. The application should either hold an
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election or appoint a different site to be 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 that elections will fail or be
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unable to complete. Calling additional elections should eventually yield a
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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 wrong site may win an election,
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resulting in the loss of some data. This is consistent with the general loss
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of data durability when running in-memory.
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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 before the environment
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is opened with the <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a>
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method. Its value cannot be changed while the environment is open.
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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()">DB->get()</a> and
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<a class="xref" href="dbcget.html" title="DBcursor->get()">DBcursor->get()</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()">DB_ENV->repmgr_start()</a> method or the
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<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</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 appears to
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have become disconnected. This option is turned on
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by default.
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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 main 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_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 group with only 2 sites. This means the client
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in a 2-site 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_elect.html" class="olink">Elections</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.
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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 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="id3928685"></a>onoff</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 <span class="bold"><strong>onoff</strong></span> parameter
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is zero, the configuration flag is turned off.
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Otherwise, it is turned on. Most configuration flags are
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turned off by default, exceptions are noted above.
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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="id3928705"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DB_ENV->rep_set_config()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h4 class="title"><a id="id3928756"></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 setting in-memory replication after the database environment is already
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opened; if setting master leases after replication is started; if setting
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the 2-site strict majority rule for a Base API application;
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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="id3928661"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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</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="id3928795"></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="rep.html#replist" title="Replication and Related Methods">Replication 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="repclockskew.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="rep.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="repset_limit.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">DB_ENV->rep_set_clockskew() </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> DB_ENV->rep_set_limit()</td>
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</tr>
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</table>
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</body>
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</html>
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