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4.2 KiB
HTML
84 lines
4.2 KiB
HTML
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
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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>Time Synchronization</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="Getting Started with Berkeley DB, Java Edition High Availability Applications" />
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<link rel="up" href="progoverview.html" title="Chapter 2. Replication API First Steps" />
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<link rel="prev" href="secondary.html" title="Secondary Nodes" />
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<link rel="next" href="two-node.html" title="Configuring Two-Node Groups" />
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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 12.2.7.5</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">Time Synchronization</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="secondary.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 2. Replication API First Steps</th>
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<td width="20%" align="right"> <a accesskey="n" href="two-node.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="timesync"></a>Time Synchronization</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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For best results, you should synchronize the clocks used by all
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machines in a replication group. If you are using a time-based
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consistency policy, this is an absolute requirement
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(see <a class="xref" href="consistency.html#timeconsistency" title="Time Consistency Policies">Time Consistency Policies</a> for more information).
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Time synchronization is easily achieved using a mechanism like <a class="ulink" href="http://www.ntp.org/" target="_top">NTPD</a>.
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</p>
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<p>
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In addition, time synchronization is also a requirement for
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internal JE HA bookkeeping. For example, JE checks for clock
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skew between the Master and a Replica
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when the Replica performs its startup handshake with the
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Master. This handshake will abort and throw
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<a class="ulink" href="../java/com/sleepycat/je/EnvironmentFailureException.html" target="_top">EnvironmentFailureException</a> if the clock skew between the
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two machines is greater than the value set for the
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<a class="ulink" href="../java/com/sleepycat/je/rep/ReplicationConfig.html#MAX_CLOCK_DELTA" target="_top">MAX_CLOCK_DELTA</a> property. This property can be set using the
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<a class="ulink" href="../java/com/sleepycat/je/rep/ReplicationConfig.html#setMaxClockDelta(long, java.util.concurrent.TimeUnit)" target="_top">ReplicationConfig.setMaxClockDelta()</a> method, or in the JE
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configuration file using the
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<code class="literal">je.rep.maxClockDelta</code> property.
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</p>
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<p>
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Finally, well synchronized clocks make it easier to correlate
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events in the logging output from different nodes in the group.
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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="secondary.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="progoverview.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="two-node.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">Secondary Nodes </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"> Configuring Two-Node Groups</td>
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</tr>
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</table>
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</div>
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</body>
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</html>
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