mirror of
https://github.com/berkeleydb/libdb.git
synced 2024-11-16 17:16:25 +00:00
281 lines
10 KiB
HTML
281 lines
10 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>Chapter 6. Summary and Examples</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 Transaction Processing" />
|
||
<link rel="up" href="index.html" title="Getting Started with Berkeley DB Transaction Processing" />
|
||
<link rel="prev" href="logconfig.html" title="Configuring the Logging Subsystem" />
|
||
<link rel="next" href="txnexample_c.html" title="Transaction Example" />
|
||
</head>
|
||
<body>
|
||
<div xmlns="" class="navheader">
|
||
<div class="libver">
|
||
<p>Library Version 11.2.5.3</p>
|
||
</div>
|
||
<table width="100%" summary="Navigation header">
|
||
<tr>
|
||
<th colspan="3" align="center">Chapter 6. Summary and Examples</th>
|
||
</tr>
|
||
<tr>
|
||
<td width="20%" align="left"><a accesskey="p" href="logconfig.html">Prev</a> </td>
|
||
<th width="60%" align="center"> </th>
|
||
<td width="20%" align="right"> <a accesskey="n" href="txnexample_c.html">Next</a></td>
|
||
</tr>
|
||
</table>
|
||
<hr />
|
||
</div>
|
||
<div class="chapter" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title"><a id="wrapup"></a>Chapter 6. Summary and Examples</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="toc">
|
||
<p>
|
||
<b>Table of Contents</b>
|
||
</p>
|
||
<dl>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="wrapup.html#anatomy">Anatomy of a Transactional Application</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="txnexample_c.html">Transaction Example</a>
|
||
</span>
|
||
</dt>
|
||
<dt>
|
||
<span class="sect1">
|
||
<a href="inmem_txnexample_c.html">In-Memory Transaction Example</a>
|
||
</span>
|
||
</dt>
|
||
</dl>
|
||
</div>
|
||
<p>
|
||
Throughout this manual we have presented the concepts and
|
||
mechanisms that you need to provide transactional protection for
|
||
your application. In this chapter, we summarize these
|
||
mechanisms, and we provide a complete example of a multi-threaded
|
||
transactional DB application.
|
||
</p>
|
||
<div class="sect1" lang="en" xml:lang="en">
|
||
<div class="titlepage">
|
||
<div>
|
||
<div>
|
||
<h2 class="title" style="clear: both"><a id="anatomy"></a>Anatomy of a Transactional Application</h2>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<p>
|
||
Transactional applications are characterized by performing the
|
||
following activities:
|
||
</p>
|
||
<div class="orderedlist">
|
||
<ol type="1">
|
||
<li>
|
||
<p>
|
||
Create your environment handle.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Open your environment, specifying that the following
|
||
subsystems be used:
|
||
</p>
|
||
<div class="itemizedlist">
|
||
<ul type="disc">
|
||
<li>
|
||
<p>
|
||
Transactional Subsystem (this also initializes the
|
||
logging subsystem).
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Memory pool (the in-memory cache).
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Logging subsystem.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Locking subsystem (if your application is multi-process or multi-threaded).
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
<p>
|
||
It is also highly recommended that you run normal recovery
|
||
upon first environment open. Normal recovery examines only those logs required
|
||
to ensure your database files are consistent relative to the information found in your
|
||
log files.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Optionally spawn off any utility threads that you might need. Utility
|
||
threads can be used to run checkpoints periodically, or to
|
||
periodically run a deadlock detector if you do not want to
|
||
use DB's built-in deadlock detector.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Open whatever database handles that you need.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Spawn off worker threads. How many of these you need and
|
||
how they split their DB workload is entirely up to your
|
||
application's requirements. However, any worker threads
|
||
that perform write operations will do the following:
|
||
</p>
|
||
<div class="orderedlist">
|
||
<ol type="a">
|
||
<li>
|
||
<p>
|
||
Begin a transaction.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Perform one or more read and write
|
||
operations.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Commit the transaction if all goes well.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Abort and retry the operation if a deadlock is
|
||
detected.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Abort the transaction for most other errors.
|
||
</p>
|
||
</li>
|
||
</ol>
|
||
</div>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
On application shutdown:
|
||
</p>
|
||
<div class="orderedlist">
|
||
<ol type="a">
|
||
<li>
|
||
<p>
|
||
Make sure there are no opened cursors.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Make sure there are no active transactions. Either
|
||
abort or commit all transactions before shutting
|
||
down.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Close your databases.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Close your environment.
|
||
</p>
|
||
</li>
|
||
</ol>
|
||
</div>
|
||
</li>
|
||
</ol>
|
||
</div>
|
||
<div class="note" style="margin-left: 0.5in; margin-right: 0.5in;">
|
||
<h3 class="title">Note</h3>
|
||
<p>
|
||
Robust DB applications should monitor their worker threads to
|
||
make sure they have not died unexpectedly. If a thread does
|
||
terminate abnormally, you must shutdown all your worker threads
|
||
and then run normal recovery (you will have to reopen your
|
||
environment to do this). This is the only way to clear any
|
||
resources (such as a lock or a mutex) that the abnormally
|
||
exiting worker thread might have been holding at the time that
|
||
it died.
|
||
</p>
|
||
<p>
|
||
Failure to perform this recovery can cause your
|
||
still-functioning worker threads to eventually block forever
|
||
while waiting for a lock that will never be released.
|
||
</p>
|
||
</div>
|
||
<p>
|
||
In addition to these activities, which are all entirely handled by
|
||
code within your application, there are some administrative
|
||
activities that you should perform:
|
||
</p>
|
||
<div class="itemizedlist">
|
||
<ul type="disc">
|
||
<li>
|
||
<p>
|
||
Periodically checkpoint your application. Checkpoints will
|
||
reduce the time to run recovery in the event that one is
|
||
required. See <a class="xref" href="filemanagement.html#checkpoints" title="Checkpoints">Checkpoints</a>
|
||
for details.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
Periodically back up your database and log files. This is
|
||
required in order to fully obtain the durability guarantee
|
||
made by DB's transaction ACID support. See
|
||
<a class="xref" href="backuprestore.html" title="Backup Procedures">Backup Procedures</a>
|
||
for more information.
|
||
</p>
|
||
</li>
|
||
<li>
|
||
<p>
|
||
You may want to maintain a hot failover if 24x7 processing
|
||
with rapid restart in the face of a disk hit is important
|
||
to you. See <a class="xref" href="hotfailover.html" title="Using Hot Failovers">Using Hot Failovers</a>
|
||
for more information.
|
||
</p>
|
||
</li>
|
||
</ul>
|
||
</div>
|
||
</div>
|
||
</div>
|
||
<div class="navfooter">
|
||
<hr />
|
||
<table width="100%" summary="Navigation footer">
|
||
<tr>
|
||
<td width="40%" align="left"><a accesskey="p" href="logconfig.html">Prev</a> </td>
|
||
<td width="20%" align="center"> </td>
|
||
<td width="40%" align="right"> <a accesskey="n" href="txnexample_c.html">Next</a></td>
|
||
</tr>
|
||
<tr>
|
||
<td width="40%" align="left" valign="top">Configuring the Logging Subsystem </td>
|
||
<td width="20%" align="center">
|
||
<a accesskey="h" href="index.html">Home</a>
|
||
</td>
|
||
<td width="40%" align="right" valign="top"> Transaction Example</td>
|
||
</tr>
|
||
</table>
|
||
</div>
|
||
</body>
|
||
</html>
|