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270 lines
13 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>DB_ENV->remove()</title>
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<link rel="stylesheet" href="apiReference.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 C API Reference" />
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<link rel="up" href="env.html" title="Chapter 5. The DB_ENV Handle" />
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<link rel="prev" href="envopen.html" title="DB_ENV->open()" />
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<link rel="next" href="envset_alloc.html" title="DB_ENV->set_alloc()" />
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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 11.2.5.3</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">DB_ENV->remove()</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="envopen.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 5.
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The DB_ENV Handle
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="envset_alloc.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="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="envremove"></a>DB_ENV->remove()</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">#include <db.h>
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int
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DB_ENV->remove(DB_ENV *dbenv, char *db_home, u_int32_t flags); </pre>
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<p>
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The <code class="methodname">DB_ENV->remove()</code> method destroys a Berkeley DB environment if it
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is not currently in use. The environment regions, including any
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backing files, are removed. Any log or database files and the
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environment directory are not removed.
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</p>
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<p>
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If there are processes that have called
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<a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a> without calling
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<a class="xref" href="envclose.html" title="DB_ENV->close()">DB_ENV->close()</a> (that
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is, there are processes currently using the environment),
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<code class="methodname">DB_ENV->remove()</code> will fail without further action unless the
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<a class="link" href="envremove.html#envremove_DB_FORCE">DB_FORCE</a> flag is set,
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in which case <code class="methodname">DB_ENV->remove()</code> will attempt to remove the
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environment, regardless of any processes still using it.
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</p>
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<p>
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The result of attempting to forcibly destroy the environment when it
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is in use is unspecified. Processes using an environment often
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maintain open file descriptors for shared regions within it. On UNIX
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systems, the environment removal will usually succeed, and processes
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that have already joined the region will continue to run in that
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region without change. However, processes attempting to join the
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environment will either fail or create new regions. On other systems
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in which the <span class="bold"><strong>unlink</strong></span>(2) system call
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will fail if any process has an open file descriptor for the file (for
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example Windows/NT), the region removal will fail.
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</p>
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<p>
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Calling <code class="methodname">DB_ENV->remove()</code> should not be necessary for most
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applications because the Berkeley DB environment is cleaned up as part
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of normal database recovery procedures. However, applications may want
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to call <code class="methodname">DB_ENV->remove()</code> as part of application shut down to free up
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system resources. For example, if the
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<a class="link" href="envopen.html#envopen_DB_SYSTEM_MEM">DB_SYSTEM_MEM</a> flag
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was specified to <a class="xref" href="envopen.html" title="DB_ENV->open()">DB_ENV->open()</a>,
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it may be useful to call <code class="methodname">DB_ENV->remove()</code> in order to release system shared memory
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segments that have been allocated. Or, on architectures in which
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mutexes require allocation of underlying system resources, it may be
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useful to call <code class="methodname">DB_ENV->remove()</code> in order to release those resources.
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Alternatively, if recovery is not required because no database state
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is maintained across failures, and no system resources need to be
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released, it is possible to clean up an environment by simply removing
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all the Berkeley DB files in the database environment's directories.
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</p>
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<p>
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In multithreaded applications, only a single thread may call the
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<code class="methodname">DB_ENV->remove()</code> method.
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</p>
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<p>
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A <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a> handle that has
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already been used to open an environment should not be used to call
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the <code class="methodname">DB_ENV->remove()</code> method; a new <a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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handle should be created for that purpose.
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</p>
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<p>
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After <code class="methodname">DB_ENV->remove()</code> has been called, regardless of its return, the
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Berkeley DB environment handle may not be accessed again.
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</p>
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<p>
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The <code class="methodname">DB_ENV->remove()</code> <span>
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<span>
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method returns a non-zero error value on failure and 0 on success.
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</span>
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</span>
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</p>
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<div class="sect2" 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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<h3 class="title"><a id="idp59649088"></a>Parameters</h3>
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</div>
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</div>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp59651192"></a>db_home</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>db_home</strong></span> parameter names the
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database environment to be removed.
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</p>
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<p>
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When using a Unicode build on Windows (the default), the <span class="bold"><strong>db_home</strong></span> argument will be interpreted as a UTF-8
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string, which is equivalent to ASCII for Latin characters.
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</p>
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</div>
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<div class="sect3" 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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<h4 class="title"><a id="idp59712136"></a>flags</h4>
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</div>
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</div>
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</div>
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<p>
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The <span class="bold"><strong>flags</strong></span> parameter must be set to 0 or by
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bitwise inclusively <span class="bold"><strong>OR</strong></span>'ing together one or more of the
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following values:
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</p>
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<div class="itemizedlist">
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<ul type="disc">
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<li>
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<p><a id="envremove_DB_FORCE"></a>
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<code class="literal">DB_FORCE</code>
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</p>
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<p>
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If set, the environment is removed, regardless of any
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processes that may still using it, and no locks are acquired during this
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process. (Generally, this flag is specified only when applications were
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unable to shut down cleanly, and there is a risk that an application may have
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died holding a Berkeley DB lock.)
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</p>
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</li>
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<li>
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<p><a id="envremove_DB_USE_ENVIRON"></a>
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<code class="literal">DB_USE_ENVIRON</code>
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</p>
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<p>
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The Berkeley DB process' environment may be permitted to specify information to
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be used when naming files; see
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<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>.
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Because permitting users to specify which files are used can create security
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problems, environment information will be used in file naming for all users
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only if the <code class="literal">DB_USE_ENVIRON</code> flag is set.
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</p>
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</li>
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<li>
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<p><a id="envremove_DB_USE_ENVIRON_ROOT"></a>
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<code class="literal">DB_USE_ENVIRON_ROOT</code>
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</p>
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<p>
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The Berkeley DB process' environment may be permitted to specify information to
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be used when naming files; see
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<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>.
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Because permitting users to specify which files are used can create security
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problems, if the <code class="literal">DB_USE_ENVIRON_ROOT</code> flag is set, environment
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information will be used in file naming only for users with appropriate
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permissions (for example, users with a user-ID of 0 on <code class="literal">UNIX</code>
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systems).
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</p>
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</li>
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</ul>
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</div>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp59703664"></a>Errors</h3>
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</div>
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</div>
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</div>
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<p>
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The <code class="methodname">DB_ENV->remove()</code> <span>
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<span>
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method may fail and return one of the following non-zero errors:
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</span>
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</span>
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</p>
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<div class="sect3" 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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<h4 class="title"><a id="idp59752656"></a>EBUSY</h4>
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</div>
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</div>
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</div>
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<p>
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The shared memory region was in use and the force flag was not set.
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</p>
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</div>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp59751328"></a>Class</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="link" href="env.html" title="Chapter 5. The DB_ENV Handle">DB_ENV</a>
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</p>
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</div>
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<div class="sect2" 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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<h3 class="title"><a id="idp59748304"></a>See Also</h3>
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</div>
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</div>
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</div>
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<p>
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<a class="xref" href="env.html#envlist" title="Database Environments and Related Methods">Database Environments and Related Methods</a>
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</p>
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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="envopen.html">Prev</a> </td>
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<td width="20%" align="center">
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<a accesskey="u" href="env.html">Up</a>
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</td>
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<td width="40%" align="right"> <a accesskey="n" href="envset_alloc.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">DB_ENV->open() </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"> DB_ENV->set_alloc()</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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