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<title>Berkeley DB Reference Guide: Connecting to a new site</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Berkeley DB Replication</dl></h3></td>
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<h1 align=center>Connecting to a new site</h1>
<p>Connecting to a new site in the replication group happens whenever the
<a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> function returns <a href="../../api_c/rep_message.html#DB_REP_NEWSITE">DB_REP_NEWSITE</a>. The application
should assign the new site a local environment ID number, and all future
messages from the site passed to <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> should include that
environment ID number. It is possible, of course, for the application
to be aware of a new site before the return of <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> (for
example, applications using connection-oriented protocols are likely to
detect new sites immediately, while applications using broadcast
protocols may not).
<p>Regardless, in applications supporting the dynamic addition of database
environments to replication groups, environments joining an existing
replication group may need to provide contact information. (For
example, in an application using TCP/IP sockets, a DNS name or IP
address might be a reasonable value to provide.) This can be done using
the <b>cdata</b> parameter to the <a href="../../api_c/rep_start.html">DB_ENV->rep_start</a> function. The information
referenced by <b>cdata</b> is wrapped in the initial contact message
sent by the new environment, and is provided to the existing members of
the group using the <b>rec</b> parameter returned by <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a>.
If no additional information was provided for Berkeley DB to forward to the
existing members of the group, the <b>data</b> field of the <b>rec</b>
parameter passed to the <a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> function will be NULL after
<a href="../../api_c/rep_message.html">DB_ENV->rep_process_message</a> returns <a href="../../api_c/rep_message.html#DB_REP_NEWSITE">DB_REP_NEWSITE</a>.
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