mirror of
https://github.com/berkeleydb/je.git
synced 2024-11-15 01:46:24 +00:00
89 lines
4.9 KiB
HTML
89 lines
4.9 KiB
HTML
|
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
|
|||
|
|
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
|
|||
|
|
<html xmlns="http://www.w3.org/1999/xhtml">
|
|||
|
|
<head>
|
|||
|
|
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
|
|||
|
|
<title>Checkpoints</title>
|
|||
|
|
<link rel="stylesheet" href="gettingStarted.css" type="text/css" />
|
|||
|
|
<meta name="generator" content="DocBook XSL Stylesheets V1.73.2" />
|
|||
|
|
<link rel="start" href="index.html" title="Getting Started with Berkeley DB, Java Edition Transaction Processing" />
|
|||
|
|
<link rel="up" href="jebackuprestore.html" title="Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications" />
|
|||
|
|
<link rel="prev" href="jebackuprestore.html" title="Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications" />
|
|||
|
|
<link rel="next" href="backup.html" title="Performing Backups" />
|
|||
|
|
</head>
|
|||
|
|
<body>
|
|||
|
|
<div xmlns="" class="navheader">
|
|||
|
|
<div class="libver">
|
|||
|
|
<p>Library Version 12.2.7.5</p>
|
|||
|
|
</div>
|
|||
|
|
<table width="100%" summary="Navigation header">
|
|||
|
|
<tr>
|
|||
|
|
<th colspan="3" align="center">Checkpoints</th>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="20%" align="left"><a accesskey="p" href="jebackuprestore.html">Prev</a> </td>
|
|||
|
|
<th width="60%" align="center">Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications</th>
|
|||
|
|
<td width="20%" align="right"> <a accesskey="n" href="backup.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
<hr />
|
|||
|
|
</div>
|
|||
|
|
<div class="sect1" lang="en" xml:lang="en">
|
|||
|
|
<div class="titlepage">
|
|||
|
|
<div>
|
|||
|
|
<div>
|
|||
|
|
<h2 class="title" style="clear: both"><a id="chkpoint"></a>Checkpoints</h2>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
Running normal recovery can become expensive if over time all that is ever
|
|||
|
|
written to disk is BTree leaf nodes. So in order to limit the time required for normal recovery, JE runs
|
|||
|
|
checkpoints. Checkpoints write to your log files all the internal BTree nodes and structures modified as a part of
|
|||
|
|
write operations. This means that your log files contain a complete BTree up to
|
|||
|
|
the moment in time when the checkpoint was run. The result is that normal recovery only needs to recreate the
|
|||
|
|
portion of the BTree that has been modified since the time of the last checkpoint.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Checkpoints typically write more information to disk than do transaction commits, and so they are more
|
|||
|
|
expensive from a disk I/O perspective. You will therefore need to consider how frequently to run checkpoints
|
|||
|
|
as a part of your performance tuning activities. When you do this, balance the cost of the checkpoints
|
|||
|
|
against the time it will take your application to restart due to the cost of running normal recovery.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Checkpoints are normally performed by the checkpointer background thread, which is always running. Like
|
|||
|
|
all background threads, it is managed using the <code class="filename">je.properties</code> file. Currently, the
|
|||
|
|
only checkpointer property that you may want to manage is
|
|||
|
|
<code class="literal">je.checkpointer.bytesInterval</code>. This property identifies how much JE's log files
|
|||
|
|
can grow before a checkpoint is run. Its value is specified in bytes. Decreasing this value causes the
|
|||
|
|
checkpointer thread to run checkpoints more frequently. This will improve the time that it takes to run
|
|||
|
|
recovery, but it also increases the system resources (notably, I/O) required by JE.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
Note that checkpoints are also always performed when the environment is closed normally. Therefore,
|
|||
|
|
normal recovery only has work to do if the application crashes or otherwise ends abnormally without
|
|||
|
|
calling <code class="methodname">Environment.close()</code>.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
<div class="navfooter">
|
|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="jebackuprestore.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="jebackuprestore.html">Up</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="backup.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top">Chapter 5. Backing up and Restoring Berkeley DB, Java Edition Applications </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top"> Performing Backups</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|