File: //proc/2/task/2/root/usr/share/doc/db4-devel-4.3.29/ref/am_misc/perm.html
<!--$Id: perm.so,v 1.4 2002/06/20 12:53:58 bostic Exp $-->
<!--Copyright 1997-2004 by Sleepycat Software, Inc.-->
<!--All rights reserved.-->
<!--See the file LICENSE for redistribution information.-->
<html>
<head>
<title>Berkeley DB Reference Guide: Retrieved key/data permanence for C/C++</title>
<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++">
</head>
<body bgcolor=white>
<a name="2"><!--meow--></a><a name="3"><!--meow--></a>
<table width="100%"><tr valign=top>
<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></h3></td>
<td align=right><a href="../am_misc/struct.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../am_misc/error.html"><img src="../../images/next.gif" alt="Next"></a>
</td></tr></table>
<p>
<h3 align=center>Retrieved key/data permanence for C/C++</h3>
<p>When using the non-cursor Berkeley DB calls to retrieve key/data items under
the C/C++ APIs (for example, <a href="../../api_c/db_get.html">DB->get</a>), the memory to which the
pointer stored into the <a href="../../api_c/dbt_class.html">DBT</a> refers is only valid until the next
call to Berkeley DB using the <a href="../../api_c/db_class.html">DB</a> handle. (This includes <b>any</b>
use of the returned <a href="../../api_c/db_class.html">DB</a> handle, including by another thread of
control within the process. For this reason, when multiple threads are
using the returned <a href="../../api_c/db_class.html">DB</a> handle concurrently, one of the
<a href="../../api_c/dbt_class.html#DB_DBT_MALLOC">DB_DBT_MALLOC</a>, <a href="../../api_c/dbt_class.html#DB_DBT_REALLOC">DB_DBT_REALLOC</a> or <a href="../../api_c/dbt_class.html#DB_DBT_USERMEM">DB_DBT_USERMEM</a>
flags must be specified with any non-cursor <a href="../../api_c/dbt_class.html">DBT</a> used for key or
data retrieval.)</p>
<p>When using the cursor Berkeley DB calls to retrieve key/data items under the
C/C++ APIs (for example, <a href="../../api_c/dbc_get.html">DBcursor->c_get</a>), the memory to which the
pointer stored into the <a href="../../api_c/dbt_class.html">DBT</a> refers is only valid until the next
call to Berkeley DB using the <a href="../../api_c/dbc_class.html">DBC</a> handle returned by <a href="../../api_c/db_cursor.html">DB->cursor</a>.</p>
<table width="100%"><tr><td><br></td><td align=right><a href="../am_misc/struct.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../am_misc/error.html"><img src="../../images/next.gif" alt="Next"></a>
</td></tr></table>
<p><font size=1><a href="../../sleepycat/legal.html">Copyright (c) 1996-2004</a> <a href="http://www.sleepycat.com">Sleepycat Software, Inc.</a> - All rights reserved.</font>
</body>
</html>