mirror of
https://github.com/berkeleydb/je.git
synced 2024-08-03 21:09:28 +00:00
177 lines
7.4 KiB
HTML
177 lines
7.4 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>Application Requirements</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="introduction.html" title="Chapter 1. Introduction" />
|
||
<link rel="prev" href="sysfailure.html" title="A Note on System Failure" />
|
||
<link rel="next" href="multithread-intro.html" title="Multi-threaded Applications" />
|
||
</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">Application Requirements</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="sysfailure.html">Prev</a> </td>
|
||
<th width="60%" align="center">Chapter 1. Introduction</th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="multithread-intro.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="apireq"></a>Application Requirements</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
In order to use transactions, your application has certain
|
||
requirements beyond what is required of non-transactional protected
|
||
applications. They are:
|
||
</p>
|
||
<div class="itemizedlist">
|
||
<ul type="disc">
|
||
<li>
|
||
<p>
|
||
Transaction subsystem.
|
||
</p>
|
||
<p>
|
||
In order to use transactions, you must explicitly
|
||
enable the transactional subsystem for your
|
||
application, and this must be done at the time that
|
||
your environment is first created.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
|
||
|
||
<span>Transaction</span>
|
||
|
||
handles.
|
||
</p>
|
||
<p>
|
||
In order to obtain the atomicity guarantee offered by
|
||
the transactional subsystem (that is, combine multiple
|
||
operations in a single unit of work), your application must use
|
||
transaction handles. These handles are obtained from your
|
||
|
||
|
||
|
||
<span>Environment</span>
|
||
objects. They should normally be short-lived, and their usage is
|
||
reasonably simple. To complete a transaction and save
|
||
the work it performed, you
|
||
call its <code class="methodname">commit()</code> method. To
|
||
complete a transaction and discard its work, you call its
|
||
<code class="methodname">abort()</code> method.
|
||
</p>
|
||
<p>
|
||
In addition, it is possible to use auto commit if you want
|
||
to transactional protect a single write operation. Auto
|
||
commit allows a transaction to be used without
|
||
obtaining an explicit transaction handle. See
|
||
<a class="xref" href="autocommit.html" title="Auto Commit">Auto Commit</a>
|
||
for information on how to use auto commit.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Entity Store
|
||
</p>
|
||
<p>
|
||
If you are using the DPL, then you must
|
||
configure your entity stores for transactional
|
||
support before opening them (that is, before
|
||
obtaining a primary index from them for the first
|
||
time).
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Database open requirements.
|
||
</p>
|
||
<p>
|
||
|
||
|
||
<span>Your</span>
|
||
|
||
application must transaction protect the database
|
||
|
||
opens<span>,
|
||
and any secondary index associations,</span>
|
||
|
||
if subsequent operations on the databases are to be transaction
|
||
protected. The database open and secondary index
|
||
association are commonly transaction protected using
|
||
auto commit.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Deadlock detection.
|
||
</p>
|
||
<p>
|
||
Typically transactional applications use multiple
|
||
threads of control when accessing the database.
|
||
Any time multiple threads are used on a single resource,
|
||
the potential for lock contention arises. In turn, lock
|
||
contention can lead to deadlocks. See
|
||
<a class="xref" href="blocking_deadlocks.html" title="Locks, Blocks, and Deadlocks">Locks, Blocks, and Deadlocks</a>
|
||
for more information.
|
||
</p>
|
||
<p>
|
||
Therefore, transactional applications must frequently
|
||
include code for detecting and responding to deadlocks.
|
||
Note that this requirement is not
|
||
<span class="emphasis"><em>specific</em></span> to transactions
|
||
– you can certainly write concurrent
|
||
non-transactional JE applications. Further, not
|
||
every transactional application uses concurrency and
|
||
so not every transactional application must
|
||
manage deadlocks. Still, deadlock management is so
|
||
frequently a characteristic of transactional
|
||
applications that we discuss it in this
|
||
book. See <a class="xref" href="txnconcurrency.html" title="Chapter 4. Concurrency">Concurrency</a>
|
||
for more information.
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="sysfailure.html">Prev</a> </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="u" href="introduction.html">Up</a>
|
||
</td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="multithread-intro.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">A Note on System Failure </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Multi-threaded
|
||
|
||
Applications</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|