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<h2 class="title" style="clear: both"><a id="repmgrstart"></a>DB_ENV->repmgr_start()</h2>
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<pre class="programlisting">#include <db.h>
int
DB_ENV->repmgr_start(DB_ENV *env, int nthreads, u_int32_t flags); </pre>
<p>
The <code class="methodname">DB_ENV->repmgr_start()</code> method starts the Replication Manager.
</p>
<p>
There are two ways to build Berkeley DB replication applications: the
most common approach is to use the Berkeley DB library Replication
Manager, where the Berkeley DB library manages the
replication group, including network transport, all replication
message processing and acknowledgment, and group elections.
Applications using the Replication Manager generally make the
following calls:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Use <a class="xref" href="repmgr_site.html" title="DB_ENV->repmgr_site()">DB_ENV->repmgr_site()</a>
to obtain a DB_SITE handle, then use that handle to
configure the sites in your replication group.
</p>
<div class="orderedlist">
<ol type="a">
<li>
<p>
Use <a class="xref" href="dbsite_set_config.html" title="DB_SITE->set_config()">DB_SITE->set_config()</a>
to configure sites in your replication group.
</p>
</li>
<li>
<p>
Use <a class="xref" href="dbsite_remove.html" title="DB_SITE->remove()">DB_SITE->remove()</a>
to remove a site from the replication group.
</p>
</li>
</ol>
</div>
</li>
<li>
<p>
Call
<a class="xref" href="repmgrset_ack_policy.html" title="DB_ENV->repmgr_set_ack_policy()">DB_ENV->repmgr_set_ack_policy()</a>
to configure the message acknowledgment policy which best supports the
replication group's transactional needs.
</p>
</li>
<li>
<p>
Call
<a class="xref" href="reppriority.html" title="DB_ENV->rep_set_priority()">DB_ENV->rep_set_priority()</a>
to configure the local site's election priority.
</p>
</li>
<li>
<p>
Call <code class="methodname">DB_ENV->repmgr_start()</code> to start the replication application.
</p>
</li>
</ol>
</div>
<p>
For more information on building Replication Manager applications,
please see the <em class="citetitle">Replication Getting Started Guide</em>
included in the Berkeley DB documentation.
</p>
<p>
Applications with special needs (for example, applications using
network protocols not supported by the Berkeley DB Replication
Manager), must perform additional configuration and call other
Berkeley DB replication Base API methods. For more information on building
Base API applications, please see the
<a href="../../programmer_reference/rep_base_meth.html" class="olink">Base API Methods</a> section in the
<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
</p>
<p>
Starting the Replication Manager consists of opening the TCP/IP listening socket to accept
incoming connections, and starting all necessary background threads. When multiple processes
share a database environment, only one process can open the listening socket; the
<code class="methodname">DB_ENV->repmgr_start()</code> method automatically opens the socket in the
first process to call it, and skips this step in the later calls from other processes.
</p>
<p>
The <code class="methodname">DB_ENV->repmgr_start()</code> method
may not be called before the <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> method is
called to open. In addition, this method may not be called before
your replication sites have been configured using the
<a class="link" href="db_site.html" title="The DB_SITE Handle">DB_SITE</a> class.
In addition, the local environment must be opened with the
<a class="link" href="envopen.html#envopen_DB_THREAD">DB_THREAD</a>
flag set.
</p>
<p>
The <code class="methodname">DB_ENV->repmgr_start()</code> method will return
<code class="literal">DB_REP_IGNORE</code>
as an informational, non-error return code, if another process has previously become the
TCP/IP listener (though the current call has nevertheless successfully started Replication
Manager's background threads). Unless otherwise specified, the
<code class="methodname">DB_ENV->repmgr_start()</code> <span>
<span>
method returns a non-zero error value on failure and 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp54473552"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp54481264"></a>nthreads</h4>
</div>
</div>
</div>
<p>
Specify the number of threads of control created and dedicated to
processing replication messages. In addition to these message
processing threads, the Replication Manager creates and manages a few
of its own threads of control. The TCP/IP listener
process can change this value after the Replication
Manager is started with a subsequent call to the
<code class="methodname">DB_ENV->repmgr_start()</code> method.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp54473448"></a>flags</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>flags</strong></span> parameter must be set to
one of the following values when first starting the
Replication Manager:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="repmgrstart_DB_REP_MASTER"></a>
<code class="literal">DB_REP_MASTER</code>
</p>
<p>
Start as a master site, and do not call for an election. Note there
must never be more than a single master in any replication group, and
only one site at a time should ever be started with the DB_REP_MASTER
flag specified.
</p>
</li>
<li>
<p><a id="repmgrstart_DB_REP_CLIENT"></a>
<code class="literal">DB_REP_CLIENT</code>
</p>
<p>
Start as a client site, and do not call for an election.
</p>
</li>
<li>
<p>
<code class="literal">DB_REP_ELECTION</code>
</p>
<p>
Start as a client, and call for an election if no master is found.
</p>
</li>
</ul>
</div>
<p>
If the Replication Manager is already started, a
<span class="bold"><strong>flags</strong></span> value of 0 can
be used when making a subsequent call to change the
value of <span class="bold"><strong>nthreads</strong></span>.
</p>
</div>
</div>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp54477576"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DB_ENV->repmgr_start()</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="idp54495072"></a>DB_REP_UNAVAIL</h4>
</div>
</div>
</div>
<p>
The local site tried to join the group, but was unable to do
so for some reason (because a master site is not available,
or because insufficient replicas are running to acknowledge
the new site). When that happens the application should
pause and retry adding the site until it completes
successfully.
</p>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp54481752"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
If the database environment was not already opened or was
opened without the <code class="literal">DB_THREAD</code> flag set; a local
site has not already been configured, this method is called
from 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="idp54496152"></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="idp54491800"></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>
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