greg/libdb
1
0
Fork 0
mirror of https://github.com/berkeleydb/libdb.git synced 2024-11-16 17:16:25 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions
libdb/docs/programmer_reference/env_faq.html

106 lines
5.5 KiB
HTML
Raw Permalink Normal View History

Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
<?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>Environment FAQ</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="Berkeley DB Programmer's Reference Guide" />
<link rel="up" href="env.html" title="Chapter 9.  The Berkeley DB Environment" />
<link rel="prev" href="env_remote.html" title="Remote filesystems" />
<link rel="next" href="cam.html" title="Chapter 10.  Berkeley DB Concurrent Data Store Applications" />
</head>
<body>
<div xmlns="" class="navheader">
<div class="libver">
Release 5.3.21 5/11/2012
2012-11-14 21:35:20 +00:00
<p>Library Version 11.2.5.3</p>
Release 5.2.28 on 6/10/2011
2011-09-13 17:44:24 +00:00
</div>
<table width="100%" summary="Navigation header">
<tr>
<th colspan="3" align="center">Environment FAQ</th>
</tr>
<tr>
<td width="20%" align="left"><a accesskey="p" href="env_remote.html">Prev</a> </td>
<th width="60%" align="center">Chapter 9. 
The Berkeley DB Environment
</th>
<td width="20%" align="right"> <a accesskey="n" href="cam.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="env_faq"></a>Environment FAQ</h2>
</div>
</div>
</div>
<div class="orderedlist">
<ol type="1">
<li>
<p>
<span class="bold"><strong>I'm using multiple processes to access an Berkeley DB database
environment; is there any way to ensure that two processes don't run transactional
recovery at the same time, or that all processes have exited the database
environment so that recovery can be run?</strong></span>
</p>
<p>
See <a class="xref" href="transapp_fail.html" title="Handling failure in Transactional Data Store applications">Handling failure in Transactional Data Store applications</a> and
<a class="xref" href="transapp_app.html" title="Architecting Transactional Data Store applications">Architecting Transactional Data Store applications</a> for a full
discussion of this topic.
</p>
</li>
<li>
<p>
<span class="bold"><strong>How can I associate application information with a <a href="../api_reference/C/db.html" class="olink">DB</a> or
<a href="../api_reference/C/env.html" class="olink">DB_ENV</a> handle?</strong></span>
</p>
<p>
In the C API, the <a href="../api_reference/C/db.html" class="olink">DB</a> and <a href="../api_reference/C/env.html" class="olink">DB_ENV</a> structures each contain an "app_private" field intended
to be used to reference application-specific information. See the <a href="../api_reference/C/dbcreate.html" class="olink">db_create()</a> and
<a href="../api_reference/C/envcreate.html" class="olink">db_env_create()</a> documentation for more information.
</p>
<p>
In the C++ or Java APIs, the easiest way to associate application-specific data with a
handle is to subclass the <a href="../api_reference/CXX/db.html" class="olink">Db</a> or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a>, for example subclassing
<a href="../api_reference/CXX/db.html" class="olink">Db</a> to get MyDb. Objects of type MyDb will still have the Berkeley DB API
methods available on them, and you can put any extra data or methods you want into the
MyDb class. If you are using "callback" APIs that take <a href="../api_reference/CXX/db.html" class="olink">Db</a> or
<a href="../api_reference/CXX/env.html" class="olink">DbEnv</a> arguments (for example,
<a href="../api_reference/CXX/dbset_bt_compare.html" class="olink">Db::set_bt_compare()</a>)
these will always be called with the <a href="../api_reference/CXX/db.html" class="olink">Db</a> or <a href="../api_reference/CXX/env.html" class="olink">DbEnv</a> objects you
create. So if you always use MyDb objects, you will be able to take the first argument
to the callback function and cast it to a MyDb (in C++, cast it to (MyDb*)). That will
allow you to access your data members or methods.
</p>
</li>
</ol>
</div>
</div>
<div class="navfooter">
<hr />
<table width="100%" summary="Navigation footer">
<tr>
<td width="40%" align="left"><a accesskey="p" href="env_remote.html">Prev</a> </td>
<td width="20%" align="center">
<a accesskey="u" href="env.html">Up</a>
</td>
<td width="40%" align="right"> <a accesskey="n" href="cam.html">Next</a></td>
</tr>
<tr>
<td width="40%" align="left" valign="top">Remote filesystems </td>
<td width="20%" align="center">
<a accesskey="h" href="index.html">Home</a>
</td>
<td width="40%" align="right" valign="top"> Chapter 10. 
Berkeley DB Concurrent Data Store Applications
</td>
</tr>
</table>
</div>
</body>
</html>
Reference in a new issue Copy permalink