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<h2 class="title" style="clear: both"><a id="bulk"></a>Bulk Transfers</h2>
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<p>
By default, messages are sent from the master to replicas as they are generated.
This can degrade replication performance because the various participating
environments must handle a fair amount of network I/O activity.
</p>
<p>
You can alleviate this problem by configuring your master environment for bulk
transfers. Bulk transfers simply cause replication messages to accumulate in a
buffer until a triggering event occurs. When this event occurs, the entire
contents of the buffer is sent to the replica, thereby eliminating excessive
network I/O.
</p>
<p>
Note that if you are using replica to replica transfers, then you might want any
replica that can service replication requests to also be configured for bulk
transfers.
</p>
<p>
The events that result in a bulk transfer of replication messages to a replica
will differ depending on if the transmitting environment is a master or a
replica.
</p>
<p>
If the servicing environment is a master environment, then bulk a bulk transfer
occurs when:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Bulk transfers are configured for the master environment, and
</p>
</li>
<li>
<p>
the message buffer is full or
</p>
</li>
<li>
<p>
a permanent record (for example, a transaction commit or a
checkpoint record) is placed in the buffer for the replica.
</p>
</li>
</ol>
</div>
<p>
If the servicing environment is a replica environment (that is, replica to replica
transfers are in use), then a bulk transfer occurs when:
</p>
<div class="orderedlist">
<ol type="1">
<li>
<p>
Bulk transfers are configured for the transmitting replica, and
</p>
</li>
<li>
<p>
the message buffer is full or
</p>
</li>
<li>
<p>
the replica servicing the request is able to completely satisfy
the request with the contents of the message buffer.
</p>
</li>
</ol>
</div>
<p>
To configure bulk transfers, specify
<span>
<tt class="literal">DB_REP_CONF_BULK</tt> to
<tt class="methodname">DbEnv::rep_set_config()</tt>
and then specify <tt class="literal">1</tt> to the <tt class="literal">onoff</tt>
parameter. (Specify <tt class="literal">0</tt> to turn the feature off.)
</span>
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