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390 lines
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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>berkdb env</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 TCL API Reference" />
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<link rel="up" href="tclapi.html" title="Chapter 1. Berkeley DB Tcl APIs" />
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<link rel="prev" href="env_dbrename.html" title="env dbrename" />
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<link rel="next" href="env_remove.html" title="berkdb envremove" />
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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 11.2.5.2</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">berkdb env</th>
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</tr>
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<tr>
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<td width="20%" align="left"><a accesskey="p" href="env_dbrename.html">Prev</a> </td>
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<th width="60%" align="center">Chapter 1.
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Berkeley DB Tcl APIs
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</th>
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<td width="20%" align="right"> <a accesskey="n" href="env_remove.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="env_open"></a>berkdb env</h2>
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</div>
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</div>
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</div>
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<pre class="programlisting">berkdb env
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[-cachesize {gbytes bytes ncache}]
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[-create]
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[-data_dir dirname]
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[-encryptaes passwd]
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[-encryptany passwd]
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[-errfile filename]
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[-home directory]
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[-log_dir dirname]
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[-mode mode]
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[-private]
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[-recover]
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[-recover_fatal]
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[-shm_key shmid]
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[-system_mem]
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[-tmp_dir dirname]
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[-txn [nosync]]
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[-txn_max max]
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[-use_environ]
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[-use_environ_root] </pre>
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<p>
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The <span class="bold"><strong>berkdb env</strong></span> command opens and
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optionally creates a database environment. The returned environment
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handle is bound to a Tcl command of the form <span class="bold"><strong>envN</strong></span>, where N is an integer starting at 0 (for
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example, env0 and env1). It is through this Tcl command that the
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script accesses the environment methods. The command automatically
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initializes the Shared Memory Buffer Pool subsystem. This subsystem
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is used whenever the application is using any Berkeley DB access
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method.
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</p>
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<p>
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The options are as follows:
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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>
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<span class="bold"><strong>-cachesize {gbytes bytes ncache}</strong></span>
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</p>
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<p>
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Set the size of the database's shared memory buffer pool (that is, the
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cache), to <span class="bold"><strong>gbytes</strong></span> gigabytes plus
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<span class="bold"><strong>bytes</strong></span>. The cache should be the size
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of the normal working data set of the application, with some small
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amount of additional memory for unusual situations. (Note: The working
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set is not the same as the number of simultaneously referenced pages,
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and should be quite a bit larger!)
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</p>
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<p>
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The default cache size is 256KB, and may not be specified as less than
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20KB. Any cache size less than 500MB is automatically increased by
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25% to account for buffer pool overhead; cache sizes larger than 500MB
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are used as specified.
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</p>
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<p>
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It is possible to specify caches to Berkeley DB that are large enough
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so that they cannot be allocated contiguously on some architectures;
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for example, some releases of Solaris limit the amount of memory that
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may be allocated contiguously by a process. If <span class="bold"><strong>ncache</strong></span> is 0 or 1, the cache will be allocated
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contiguously in memory. If it is greater than 1, the cache will be
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broken up into <span class="bold"><strong>ncache</strong></span> equally sized
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separate pieces of memory.
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</p>
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<p>
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For information on tuning the Berkeley DB cache size, see
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<a href="../../programmer_reference/general_am_conf.html#am_conf_cachesize" class="olink">Selecting a Cache Size</a>
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-create</strong></span>
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</p>
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<p>
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Cause Berkeley DB subsystems to create any underlying files, as
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necessary.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-data_dir dirname</strong></span>
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</p>
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<p>
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Specify the environment's data directory as described in
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<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-encryptaes passwd</strong></span>
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</p>
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<p>
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Specify the database should be encrypted with the given password using
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the Rijndael/AES (also known as the Advanced Encryption Standard and
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Federal Information Processing Standard (FIPS) 197) algorithm.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-encryptany passwd</strong></span>
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</p>
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<p>
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Specify the already existing environment should be opened with the
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given password. This option is used if the environment is known to be
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encrypted, but the specific algorithm used is not known.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-errfile filename</strong></span>
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</p>
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<p>
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When an error occurs in the Berkeley DB library, a Berkeley DB error
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or an error return value is returned by the function. In some cases,
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however, the errno value may be insufficient to completely describe
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the cause of the error especially during initial application
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debugging.
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</p>
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<p>
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The <span class="bold"><strong>-errfile</strong></span> argument is used to
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enhance the mechanism for reporting error messages to the application
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by specifying a file to be used for displaying additional Berkeley DB
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error messages. In some cases, when an error occurs, Berkeley DB will
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output an additional error message to the specified file reference.
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</p>
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<p>
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consist of the environment command name (for example, env0) and a
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colon (":"), an error string, and a trailing <newline>
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character.
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</p>
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<p>
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This error-logging enhancement does not slow performance or
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significantly increase application size, and may be run during normal
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operation as well as during application debugging.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-home directory</strong></span>
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</p>
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<p>
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The <span class="bold"><strong>-home</strong></span> argument is described in
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<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-log_dir dirname</strong></span>
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</p>
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<p>
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Specify the environment's logging file directory as described in
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<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-mode mode</strong></span>
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</p>
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<p>
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On UNIX systems, or in IEEE/ANSI Std 1003.1 (POSIX) environments, all
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files created by Berkeley DB are created with mode <span class="bold"><strong>mode</strong></span> (as described in <span class="bold"><strong>chmod</strong></span>(2)) and modified by the process' umask
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value at the time of creation (see <span class="bold"><strong>umask</strong></span>(2)). The group ownership of created
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files is based on the system and directory defaults, and is not
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further specified by Berkeley DB. If <span class="bold"><strong>mode</strong></span> is 0, files are created readable and
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writable by both owner and group. On Windows systems, the mode
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argument is ignored.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-private</strong></span>
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</p>
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<p>
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Specify that the environment will only be accessed by a single process
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(although that process may be multithreaded). This flag has two
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effects on the Berkeley DB environment. First, all underlying data
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structures are allocated from per-process memory instead of from
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shared memory that is potentially accessible to more than a single
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process. Second, mutexes are only configured to work between threads.
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</p>
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<p>
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This flag should not be specified if more than a single process is
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accessing the environment, as it is likely to cause database
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corruption and unpredictable behavior. For example, if both a server
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application and the Berkeley DB utility
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<a href="../C/db_stat.html" class="olink">db_stat</a>
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will access the environment, the <span class="bold"><strong>-private</strong></span> option
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should not be specified.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-recover</strong></span>
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</p>
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<p>
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Run normal recovery on this environment before opening it for normal
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use. If this flag is set, the <span class="bold"><strong>-create</strong></span>
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option must also be set because the regions will be removed and
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re-created.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-recover_fatal</strong></span>
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</p>
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<p>
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Run catastrophic recovery on this environment before opening it for
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normal use. If this flag is set, the <span class="bold"><strong>-create</strong></span> option must also be set since the
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regions will be removed and re-created.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-shm_key key</strong></span>
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</p>
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<p>
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Specify a base segment ID for Berkeley DB environment shared memory
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regions created in system memory on systems supporting X/Open-style
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shared memory interfaces, for example, UNIX systems supporting
|
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shmget(2) and related System V IPC interfaces. See
|
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<a href="../../programmer_reference/env_region.html" class="olink">Shared Memory Regions</a>
|
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|
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.
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</p>
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</li>
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<li>
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<p>
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<span class="bold"><strong>-system_mem</strong></span>
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</p>
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<p>
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Allocate memory from system shared memory instead of memory backed by
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the filesystem. See
|
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<a href="../../programmer_reference/env_region.html" class="olink">Shared Memory Regions</a>
|
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|
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in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em> for more information.
|
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</p>
|
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</li>
|
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<li>
|
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<p>
|
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<span class="bold"><strong>-tmp_dir dirname</strong></span>
|
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|
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</p>
|
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|
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<p>
|
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|
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Specify the environment's tmp directory, as described in
|
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|
|
<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>
|
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|
|
in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>.
|
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|
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</p>
|
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</li>
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<li>
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<p>
|
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<span class="bold"><strong>-txn [nosync]</strong></span>
|
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|
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</p>
|
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<p>
|
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Initialize the Transaction subsystem. This subsystem is used when
|
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recovery and atomicity of multiple operations and recovery are
|
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|
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important. The <span class="bold"><strong>-txn</strong></span> option implies
|
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|
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the initialization of the logging and locking subsystems as well.
|
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|
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</p>
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|
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<p>
|
|||
|
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If the optional <span class="bold"><strong>nosync</strong></span> argument is
|
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|
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specified, the log will not be synchronously flushed on transaction
|
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|
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commit. This means that transactions exhibit the ACI (atomicity,
|
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|
|
consistency, and isolation) properties, but not D (durability); that
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|||
|
|
is, database integrity will be maintained, but it is possible that
|
|||
|
|
some number of the most recently committed transactions may be undone
|
|||
|
|
during recovery instead of being redone.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
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The number of transactions that are potentially at risk is governed by
|
|||
|
|
how often the log is checkpointed (see
|
|||
|
|
<a href="../C/db_checkpoint.html" class="olink">db_checkpoint</a>
|
|||
|
|
in the <em class="citetitle">Berkeley DB C API Reference Guide</em> for more information) and how many
|
|||
|
|
log updates can fit on a single log page.
|
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|
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</p>
|
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|
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</li>
|
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|
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<li>
|
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|
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<p>
|
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|
|
<span class="bold"><strong>-txn_max max</strong></span>
|
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|
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</p>
|
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|
|
<p>
|
|||
|
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Set the maximum number of simultaneous transactions that are supported
|
|||
|
|
by the environment, which bounds the size of backing files. When
|
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|
|
there are more than the specified number of concurrent transactions,
|
|||
|
|
calls to <span class="emphasis"><em>env</em></span> <span class="bold"><strong>txn</strong></span>
|
|||
|
|
will fail (until some active transactions complete).
|
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|
|
</p>
|
|||
|
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</li>
|
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|
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<li>
|
|||
|
|
<p>
|
|||
|
|
<span class="bold"><strong>-use_environ</strong></span>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The Berkeley DB process' environment may be permitted to specify
|
|||
|
|
information to be used when naming files; see
|
|||
|
|
<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>
|
|||
|
|
in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>. Because
|
|||
|
|
permitting users to specify which files are used can create security
|
|||
|
|
problems, environment information will be used in file naming for all
|
|||
|
|
users only if the <span class="bold"><strong>-use_environ</strong></span> flag
|
|||
|
|
is set.
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
<li>
|
|||
|
|
<p>
|
|||
|
|
<span class="bold"><strong>-use_environ_root</strong></span>
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
The Berkeley DB process' environment may be permitted to specify
|
|||
|
|
information to be used when naming files; see
|
|||
|
|
<a href="../../programmer_reference/env_naming.html" class="olink">Berkeley DB File Naming</a>
|
|||
|
|
in the <em class="citetitle">Berkeley DB Programmer's Reference Guide</em>. As
|
|||
|
|
permitting users to specify which files are used can create security
|
|||
|
|
problems, if the <span class="bold"><strong>-use_environ_root</strong></span>
|
|||
|
|
flag is set, environment information will be used for file naming only
|
|||
|
|
for users with appropriate permissions (for example, users with a
|
|||
|
|
user-ID of 0 on IEEE/ANSI Std 1003.1 (POSIX) systems).
|
|||
|
|
</p>
|
|||
|
|
</li>
|
|||
|
|
</ul>
|
|||
|
|
</div>
|
|||
|
|
<p>
|
|||
|
|
The <span class="bold"><strong>berkdb env</strong></span> command returns an
|
|||
|
|
environment handle on success.
|
|||
|
|
</p>
|
|||
|
|
<p>
|
|||
|
|
In the case of error, a Tcl error is thrown.
|
|||
|
|
</p>
|
|||
|
|
</div>
|
|||
|
|
<div class="navfooter">
|
|||
|
|
<hr />
|
|||
|
|
<table width="100%" summary="Navigation footer">
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left"><a accesskey="p" href="env_dbrename.html">Prev</a> </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="u" href="tclapi.html">Up</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right"> <a accesskey="n" href="env_remove.html">Next</a></td>
|
|||
|
|
</tr>
|
|||
|
|
<tr>
|
|||
|
|
<td width="40%" align="left" valign="top"><span class="emphasis"><em>env</em></span> dbrename </td>
|
|||
|
|
<td width="20%" align="center">
|
|||
|
|
<a accesskey="h" href="index.html">Home</a>
|
|||
|
|
</td>
|
|||
|
|
<td width="40%" align="right" valign="top"> berkdb envremove</td>
|
|||
|
|
</tr>
|
|||
|
|
</table>
|
|||
|
|
</div>
|
|||
|
|
</body>
|
|||
|
|
</html>
|