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<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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<th colspan="3" align="center">DB_ENV->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>DB_ENV->rep_set_config()</h2>
</div>
</div>
</div>
<pre class="programlisting">#include <db.h>
int
DB_ENV->rep_set_config(DB_ENV *env, u_int32_t which, int onoff); </pre>
<p>
The <code class="methodname">DB_ENV->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">DB_ENV->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 DB_ENV Handle">DB_ENV</a> handle.
</p>
<p>
The <code class="methodname">DB_ENV->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="DB_ENV->open()">DB_ENV->open()</a> method.
This method should not be called to set preferred master mode or
master leases after the
<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->rep_start()</a> or
<a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">DB_ENV->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">DB_ENV->rep_set_config()</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="idp3764520"></a>Parameters</h3>
</div>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp3721728"></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="DB_ENV->rep_sync()">DB_ENV->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 do not
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="DB_ENV->open()">DB_ENV->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="DBcursor->get()">DBcursor->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="DB_ENV->repmgr_start()">DB_ENV->repmgr_start()</a> method or the
<a class="xref" href="repstart.html" title="DB_ENV->rep_start()">DB_ENV->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 fails or
becomes disconnected. This option is turned on
by default. In preferred master mode, this option
cannot be turned off.
</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 replication
process may change this configuration setting.
</p>
</li>
<li>
<p><a id="config_DB_REPMGR_CONF_PREFMAS_CLIENT"></a>
<code class="literal">DB_REPMGR_CONF_PREFMAS_CLIENT</code>
</p>
<p>
This is the client site in a two-site
replication group running in preferred master
mode. This site automatically takes over as
temporary master when the preferred master
site is unavailable. Transactions committed
on this site when it is operating as the
temporary master may be rolled back if they
conflict with preferred master transactions.
(See the
<a href="../../programmer_reference/rep_twosite.html#twosite_prefmas" class="olink">
Preferred master mode </a>
section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>
for more information.) This configuration flag may
not be set after the <a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">DB_ENV->repmgr_start()</a> method is called.
</p>
<p>
The other site in the replication group should
be specified as the preferred master site using the
<code class="literal">DB_REPMGR_CONF_PREFMAS_MASTER</code>
configuration flag.
</p>
</li>
<li>
<p><a id="config_DB_REPMGR_CONF_PREFMAS_MASTER"></a>
<code class="literal">DB_REPMGR_CONF_PREFMAS_MASTER</code>
</p>
<p>
This is the preferred master site in a two-site
replication group running in preferred master
mode. This site functions as the master
whenever its availability permits.
When this site returns to the replication
group after having been unavailable, it
synchronizes with the temporary master and
then automatically takes over as master.
Transactions committed on this site will
not be rolled back. (See the
<a href="../../programmer_reference/rep_twosite.html#twosite_prefmas" class="olink">
Preferred master mode </a>
section in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>
for more information.) This configuration flag may not
be set after the <a class="xref" href="repmgrstart.html" title="DB_ENV->repmgr_start()">DB_ENV->repmgr_start()</a> method is called.
</p>
<p>
The other site in the replication group should
be specified as the preferred master client site
using the
<code class="literal">DB_REPMGR_CONF_PREFMAS_CLIENT</code>
configuration flag.
</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 replication group with only two
sites. This means the client
in a two-site replication 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. In preferred master mode, this option cannot
be turned off.
</p>
</li>
</ul>
</div>
</div>
<div class="sect3" lang="en" xml:lang="en">
<div class="titlepage">
<div>
<div>
<h4 class="title"><a id="idp3797304"></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="idp3771936"></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="idp3721944"></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="idp3784024"></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="idp3790856"></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>
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