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Yasuhiro KIMURA
87 lines
3.8 KiB
HTML
87 lines
3.8 KiB
HTML
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<html xmlns="http://www.w3.org/1999/xhtml">
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<head>
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<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
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<title>Replication environment priorities</title>
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<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
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<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
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<link rel="start" href="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="up" href="rep.html" title="Chapter 12. Berkeley DB Replication" />
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<link rel="prev" href="rep_id.html" title="Replication environment IDs" />
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<link rel="next" href="rep_app.html" title="Building replicated applications" />
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</head>
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<body>
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<div xmlns="" class="navheader">
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<div class="libver">
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<p>Library Version 18.1.40</p>
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</div>
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<table width="100%" summary="Navigation header">
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<tr>
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<th colspan="3" align="center">Replication environment priorities</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="rep_id.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 12. Berkeley DB Replication </th>
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<td width="20%" align="right"> <a accesskey="n" href="rep_app.html">Next</a></td>
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</tr>
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</table>
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<hr />
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</div>
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<div class="sect1" lang="en" xml:lang="en">
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<div class="titlepage">
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<div>
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<div>
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<h2 class="title" style="clear: both"><a id="rep_pri"></a>Replication environment priorities</h2>
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</div>
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</div>
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</div>
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<p>
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Each database environment included in a replication group
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must have a priority, which specifies a relative ordering
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among the different environments in a replication group. This
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ordering is a factor in determining which environment will be
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selected as a new master in case the existing master fails.
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Both Replication Manager applications and Base API
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applications should specify environment priorities.
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</p>
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<p>
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Priorities are an unsigned integer, but do not need to be
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unique throughout the replication group. A priority of 0 means
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the system can never become a master. Otherwise, larger valued
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priorities indicate a more desirable master. For example, if a
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replication group consists of three database environments, two
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of which are connected by an OC3 and the third of which is
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connected by a T1, the third database environment should be
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assigned a priority value which is lower than either of the
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other two.
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</p>
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<p>
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Desirability of the master is first determined by the client
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having the most recent log records. Ties in log records are
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broken with the client priority. If both sites have the same
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log and the same priority, one is selected at random.
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</p>
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</div>
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<div class="navfooter">
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<hr />
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<table width="100%" summary="Navigation footer">
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<tr>
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<td width="40%" align="left"><a accesskey="p" href="rep_id.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="rep.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="rep_app.html">Next</a></td>
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</tr>
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<tr>
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<td width="40%" align="left" valign="top">Replication environment IDs </td>
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<td width="20%" align="center">
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<a accesskey="h" href="index.html">Home</a>
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</td>
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<td width="40%" align="right" valign="top"> Building replicated applications</td>
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</tr>
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</div>
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</body>
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</html>
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