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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<th colspan="3" align="center">DbEnv::rep_set_config()</th>
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Replication Methods
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<div class="sect1" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h2 class="title" style="clear: both"><a id="repconfig"></a>DbEnv::rep_set_config()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db_cxx.h>
int
DbEnv::rep_set_config(u_int32_t which, int onoff); </pre>
<p>
The <code class="methodname">DbEnv::rep_set_config()</code> method configures the Berkeley DB
replication subsystem.
</p>
<p>
The database environment's replication subsystem may also be
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
of the entry in that file is a single line with the string
"rep_set_config", one or more whitespace characters, and the
method <span class="bold"><strong>which</strong></span> parameter as a
string and optionally one or more whitespace characters, and the
string "on" or "off". If the optional string is omitted, the
default is "on"; for example, "rep_set_config DB_REP_CONF_NOWAIT"
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>
file is read when the database environment is opened, it will
silently overrule configuration done before that time.
</p>
<p>
The <code class="methodname">DbEnv::rep_set_config()</code> method configures a database
environment, not only operations performed using the specified
<a class="link" href="env.html" title="Chapter 5. The DbEnv Handle">DbEnv</a> handle.
</p>
<p>
The <code class="methodname">DbEnv::rep_set_config()</code> method may not be
called to set in-memory replication after the environment is
opened using the
<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a> method.
This method may also not be called to set master leases after the
<a class="xref" href="repstart.html" title="DbEnv::rep_start()">DbEnv::rep_start()</a> or
<a class="xref" href="repmgrstart.html" title="DbEnv::repmgr_start()">DbEnv::repmgr_start()</a> methods
are called. For all other <span class="bold"><strong>which</strong></span>
parameters, this method may be called at any time during the life
of the application.
</p>
<p>
The <code class="methodname">DbEnv::rep_set_config()</code> <span>
<span>
method either returns a non-zero error value or throws an
exception that encapsulates a non-zero error value on
failure, and returns 0 on success.
</span>
</span>
</p>
<div class="sect2" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h3 class="title"><a id="idp9581200"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp9581896"></a>which</h4>
</div>
</div>
</div>
<p>
The <span class="bold"><strong>which</strong></span> parameter must be set to
one of the following values:
</p>
<div class="itemizedlist">
<ul type="disc">
<li>
<p><a id="config_DB_REP_CONF_AUTOINIT"></a>
<code class="literal">DB_REP_CONF_AUTOINIT</code>
</p>
<p>
The replication master will automatically re-initialize outdated
clients. This option is turned on by default.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_BULK"></a>
<code class="literal">DB_REP_CONF_BULK</code>
</p>
<p>
The replication master sends groups of records to the clients in a
single network transfer.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_DELAYCLIENT"></a>
<code class="literal">DB_REP_CONF_DELAYCLIENT</code>
</p>
<p>
The client should delay synchronizing to a newly declared master.
Clients configured in this way will remain
unsynchronized until the application calls the
<a class="xref" href="repsync.html" title="DbEnv::rep_sync()">DbEnv::rep_sync()</a> method.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_INMEM"></a>
<code class="literal">DB_REP_CONF_INMEM</code>
</p>
<p>
Store internal replication information in memory only.
</p>
<p>
By default, replication creates files in the
environment home directory to preserve some
internal information. If this configuration flag is
turned on, replication only stores this internal
information in-memory and cannot keep persistent
state across a site crash or reboot. This results
in the following limitations:
</p>
<div class="itemizedlist">
<ul type="circle">
<li>
<p>
A master site should not reappoint itself
master immediately after crashing or
rebooting because the application would
incur a slightly higher risk of client
crashes. The former master site should
rejoin the replication group as a client.
The application should either hold an
election or appoint a different site to be
the next master.
</p>
</li>
<li>
<p>
An application has a slightly higher risk
that elections will fail or be unable to
complete. Calling additional elections
should eventually yield a winner.
</p>
</li>
<li>
<p>
An application has a slight risk that the
wrong site may win an election, resulting
in the loss of some data. This is
consistent with the general loss of data
durability when running in-memory.
</p>
</li>
<li>
<p>
Replication Manager applications will no
longer maintain group membership
information persistently on-disk. For more
information, see <a href="../../programmer_reference/rep_filename.html" class="olink">Managing Replication Files</a> in the
<em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
</p>
</li>
</ul>
</div>
<p>
This configuration flag can only be turned on
before the environment is opened with the
<a class="xref" href="envopen.html" title="DbEnv::open()">DbEnv::open()</a>
method. Its value cannot be changed while the
environment is open. All sites in the replication
group should have the same value for this
configuration flag.
</p>
</li>
<li>
<p>
<code class="literal">DB_REP_CONF_LEASE</code>
</p>
<p>
Master leases will be used for this site.
</p>
<p>
Configuring this option may result in
<code class="literal">DB_REP_LEASE_EXPIRED</code> error returns
from the <a class="xref" href="dbget.html" title="Db::get()">Db::get()</a> and
<a class="xref" href="dbcget.html" title="Dbc::get()">Dbc::get()</a> methods
when attempting to read entries from a database after the site's
master lease has expired.
</p>
<p>
This configuration flag may not be set after the
<a class="xref" href="repmgrstart.html" title="DbEnv::repmgr_start()">DbEnv::repmgr_start()</a> method or the
<a class="xref" href="repstart.html" title="DbEnv::rep_start()">DbEnv::rep_start()</a>
method is called. All sites in the replication
group should have the same value for this
configuration flag.
</p>
</li>
<li>
<p><a id="config_DB_REP_CONF_NOWAIT"></a>
<code class="literal">DB_REP_CONF_NOWAIT</code>
</p>
<p>
Berkeley DB method calls that would normally block while clients are
in recovery will return errors immediately.
</p>
</li>
<li>
<p><a id="config_DB_REPMGR_CONF_ELECTIONS"></a>
<code class="literal">DB_REPMGR_CONF_ELECTIONS</code>
</p>
<p>
Replication Manager automatically runs elections to
choose a new master when the old master appears to
have become disconnected. This option is turned on
by default.
</p>
<p>
If this option is turned off, the application is
responsible for assigning the new master
explicitly, by calling the
<code class="methodname">DB_ENV->repmgr_start()</code>
method.
</p>
<div class="caution" style="margin-left: 0.5in; margin-right: 0.5in;">
<h3 class="title">Caution</h3>
<p>
Most Replication Manager
applications should accept the default automatic
behavior. Allowing two sites in a replication
group to act as master simultaneously can lead to
loss of data.
</p>
</div>
<p>
In an application with multiple processes per
database environment, only the main replication
process may change this configuration setting.
</p>
</li>
<li>
<p><a id="config_DB_REPMGR_CONF_2SITE_STRICT"></a>
<code class="literal">DB_REPMGR_CONF_2SITE_STRICT</code>
</p>
<p>
Replication Manager observes the strict "majority" rule in managing
elections, even in a group with only 2 sites. This means the client
in a 2-site group will be unable to take over as master if the
original master fails or becomes disconnected. (See the
<a href="../../programmer_reference/rep_twosite.html" class="olink">
Special considerations for two-site replication groups
</a>
section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.)
Both sites in the replication group should have the same value for this
configuration flag. This option is turned on by
default.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp9607624"></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="idp9586856"></a>Errors</h3>
</div>
</div>
</div>
<p>
The <code class="methodname">DbEnv::rep_set_config()</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="idp9604056"></a>EINVAL</h4>
</div>
</div>
</div>
<p>
If setting in-memory replication after the database environment is already
opened; if setting master leases after replication is started; if setting
the 2-site strict majority rule 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="idp9620456"></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="idp9611272"></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>
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