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Yasuhiro KIMURA
169 lines
7.1 KiB
HTML
169 lines
7.1 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>Chapter 13. Berkeley DB Slice Support</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="index.html" title="Berkeley DB Programmer's Reference Guide" />
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<link rel="prev" href="rep_ex_chan.html" title="Ex_rep_chan: a Replication Manager channel example" />
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<link rel="next" href="slice-apis.html" title="Slice APIs" />
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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">Chapter 13. Berkeley DB Slice Support</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_ex_chan.html">Prev</a> </td>
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<th width="60%" align="center"> </th>
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<td width="20%" align="right"> <a accesskey="n" href="slice-apis.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="chapter" 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"><a id="bdb_slices"></a>Chapter 13. Berkeley DB Slice Support</h2>
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</div>
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</div>
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</div>
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<div class="toc">
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<p>
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<b>Table of Contents</b>
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</p>
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<dl>
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<dt>
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<span class="sect1">
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<a href="bdb_slices.html#slice-enable">Enabling Slices</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="slice-apis.html">Slice APIs</a>
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</span>
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</dt>
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<dt>
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<span class="sect1">
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<a href="slice-keys.html">Key Design</a>
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</span>
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</dt>
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</dl>
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</div>
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<p>
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It is possible to improve the multiprocessor scaling of your DB
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databases by implementing <span class="emphasis"><em>slices</em></span>. Slices cause
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your database records to be spread evenly across sub-environments
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and sub-databases using an internal hashing algorithm. Because your
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records are stored in separate physical environments and databases,
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this allows for better parallel processing support by spreading read and
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write workloads across separate, discrete processor cores.
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</p>
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<p>
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To use slices, you must enable slice support for your library at
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compile time. You must also configure your environment and database
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to support slices. Optionally, you can also indicate which portion
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of your keys are <span class="emphasis"><em>slice-relevant</em></span>; that is,
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which portions of your keys are used to determine which slice they
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belong to.
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</p>
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<p>
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Be aware that use of slices has some ramifications when it comes to transactional
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processing of of multiple records within a single transaction.
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Because your records are distributed not just across physical
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databases, but also across physical environments, atomic operations
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can only be performed on records contained within the same physical
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slice.
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</p>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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Slices are only supported for databases using the BTree and
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Hash access methods. Also, slices are not supported for
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in-memory only databases, or for sub-databases.
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</p>
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</div>
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<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
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<h3 class="title">Note</h3>
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<p>
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Slices are not supported for Windows in this release.
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</p>
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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="slice-enable"></a>Enabling Slices</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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To create a sliced database, do all of the following:
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</p>
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<div class="orderedlist">
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<ol type="1">
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<li>
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<p>
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Enable slices when you compile your DB library. Use
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the <code class="literal">--enable-slices</code> configuration
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option when compiling a *nix version of the library.
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</p>
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</li>
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<li>
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<p>
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Configure slice support for your environment using the
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<a href="../api_reference/C/set_slice_count_parameter.html" class="olink">set_slice_count</a> DB_CONFIG parameter. This
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parameter simply identifies the total number of slices
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you want to use. For best performance, the number of
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slices you configure should be equal to the number of
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cores available on your platform.
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</p>
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<p>
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Because using slices means that a sub-environment is created
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for each slice, it is sometimes necessary to perform
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configuration on a sub-environment basis. You can do this using
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the <a href="../api_reference/C/slice_parameter.html" class="olink">slice</a> DB_CONFIG parameter.
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</p>
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</li>
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<li>
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<p>
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Open your database so that it supports slices. Use the
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<code class="literal">DB_SLICED</code> flag with the <a href="../api_reference/C/dbopen.html" class="olink">DB->open()</a>
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method to do this. Note that this flag is only required
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when you initially create the database. After that,
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using the database will be open with sliced support
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regardless of whether the flag is present.
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</p>
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</li>
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</ol>
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</div>
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</div>
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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_ex_chan.html">Prev</a> </td>
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||
<td width="20%" align="center"> </td>
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<td width="40%" align="right"> <a accesskey="n" href="slice-apis.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">Ex_rep_chan: a Replication Manager channel example </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"> Slice APIs</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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