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| <title>Chapter 12. Distributed Persistence</title><link rel="stylesheet" href="css/docbook.css" type="text/css"><meta name="generator" content="DocBook XSL Stylesheets V1.72.0"><link rel="start" href="manual.html" title="Apache OpenJPA User's Guide"><link rel="up" href="ref_guide.html" title="Part 3. Reference Guide"><link rel="prev" href="ref_guide_event.html" title="2. Remote Event Notification Framework"><link rel="next" href="Features and Limitations.html" title="2. Salient Features"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="3" align="center">Chapter 12. |
| Distributed Persistence |
| </th></tr><tr><td width="20%" align="left"><a accesskey="p" href="ref_guide_event.html">Prev</a> </td><th width="60%" align="center">Part 3. Reference Guide</th><td width="20%" align="right"> <a accesskey="n" href="Features and Limitations.html">Next</a></td></tr></table><hr></div><div class="chapter" lang="en" id="ref_guide_slice"><div class="titlepage"><div><div><h2 class="title"><a name="ref_guide_slice"></a>Chapter 12. |
| Distributed Persistence |
| </h2></div><div><h2 class="title"><a name="ref_guide_slice"></a>Chapter 12. |
| Distributed Persistence |
| </h2></div></div></div><div class="toc"><p><b>Table of Contents</b></p><dl><dt><span class="section"><a href="ref_guide_slice.html#slice_overview">1. Overview</a></span></dt><dt><span class="section"><a href="Features and Limitations.html">2. Salient Features</a></span></dt><dd><dl><dt><span class="section"><a href="Features and Limitations.html#d0e30020">2.1. Transparency</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#d0e30028">2.2. Custom Distribution Policy</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#d0e30057">2.3. Heterogeneous Database</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#d0e30062">2.4. Parallel Execution</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#d0e30067">2.5. Distributed Query</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#d0e30101">2.6. Targeted Query</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#d0e30118">2.7. Distributed Transaction</a></span></dt><dt><span class="section"><a href="Features and Limitations.html#collocation_constraint">2.8. Collocation Constraint</a></span></dt></dl></dd><dt><span class="section"><a href="slice_configuration.html">3. Usage</a></span></dt><dd><dl><dt><span class="section"><a href="slice_configuration.html#d0e30155">3.1. How to activate Slice Runtime?</a></span></dt><dt><span class="section"><a href="slice_configuration.html#d0e30166">3.2. How to configure each database slice?</a></span></dt><dt><span class="section"><a href="slice_configuration.html#distribution_policy">3.3. Implement DistributionPolicy interface</a></span></dt><dt><span class="section"><a href="slice_configuration.html#d0e30280">3.4. </a></span></dt></dl></dd><dt><span class="section"><a href="ch26s04.html">4. Global Properties</a></span></dt><dd><dl><dt><span class="section"><a href="ch26s04.html#d0e30294">4.1. openjpa.slice.DistributionPolicy</a></span></dt><dt><span class="section"><a href="ch26s04.html#d0e30308">4.2. openjpa.slice.Lenient</a></span></dt><dt><span class="section"><a href="ch26s04.html#d0e30324">4.3. openjpa.slice.Master</a></span></dt><dt><span class="section"><a href="ch26s04.html#d0e30336">4.4. openjpa.slice.Names</a></span></dt><dt><span class="section"><a href="ch26s04.html#d0e30351">4.5. openjpa.slice.ThreadingPolicy</a></span></dt><dt><span class="section"><a href="ch26s04.html#d0e30422">4.6. openjpa.slice.TransactionPolicy</a></span></dt></dl></dd><dt><span class="section"><a href="ch26s05.html">5. Per-Slice Properties</a></span></dt></dl></div><p> |
| The standard JPA runtime environment works with a <span class="emphasis"><em>single</em></span> |
| database instance. OpenJPA can be extended via plug-in to work with |
| multiple databases within the same transaction without any change to the |
| existing application. This capability of OpenJPA for distributed |
| database environment is called <span class="emphasis"><em>Slice</em></span> and is explained in |
| the following sections. |
| </p><div class="section" lang="en"><div class="titlepage"><div><div><h2 class="title" style="clear: both"><a name="slice_overview"></a>1. Overview</h2></div></div></div><p> |
| Enterprise applications are increasingly deployed for distributed database |
| environments. The reasons for distributed, often horizontally-partitioned |
| database environment can be to counter massive data growth, to |
| support multiple external clients on a hosted platform or many other |
| practical scenarios that can benefit from data partitioning. |
| </p><p> |
| Any JPA-based user application has to address serious technical and conceptual |
| challenges to directly interact with a set of physical databases |
| within a single transaction. |
| Slice encapsulates the complexity of distributed database environment |
| via the abstraction of <span class="emphasis"><em>virtual</em></span> database which internally |
| manages multiple physical databases. We refer each physical database instance |
| as <span class="emphasis"><em>slice</em></span>. |
| <span class="emphasis"><em>Virtualization</em></span> of distributed databases |
| makes OpenJPA object management kernel and |
| the user application to work in the same way as in the case of a single physical |
| database. |
| </p></div><p> |
| The properties to configure Slice can be classified in two broad groups. |
| The <span class="emphasis"><em>global</em></span> properties apply to all the slices, for example, |
| the thread pool used to execute the queries in parallel or the transaction |
| manager used to coordinate transaction across multiple slices. |
| The <span class="emphasis"><em>per-slice</em></span> properties apply to individual slice, for example, |
| the JDBC connection URL of a slice. |
| </p></div><div class="navfooter"><hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="ref_guide_event.html">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="ref_guide.html">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="Features and Limitations.html">Next</a></td></tr><tr><td width="40%" align="left" valign="top">2. |
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