1<!--$Id: perm.so,v 1.4 2002/06/20 12:53:58 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB Reference Guide: Retrieved key/data permanence for C/C++</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<a name="2"><!--meow--></a><a name="3"><!--meow--></a> 12<table width="100%"><tr valign=top> 13<td><b><dl><dt>Berkeley DB Reference Guide:<dd>Access Methods</dl></b></td> 14<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> 15</td></tr></table> 16<p align=center><b>Retrieved key/data permanence for C/C++</b></p> 17<p>When using the non-cursor Berkeley DB calls to retrieve key/data items under 18the C/C++ APIs (for example, <a href="../../api_c/db_get.html">DB->get</a>), the memory to which the 19pointer stored into the <a href="../../api_c/dbt_class.html">DBT</a> refers is only valid until the next 20call to Berkeley DB using the <a href="../../api_c/db_class.html">DB</a> handle. (This includes <b>any</b> 21use of the returned <a href="../../api_c/db_class.html">DB</a> handle, including by another thread of 22control within the process. For this reason, when multiple threads are 23using the returned <a href="../../api_c/db_class.html">DB</a> handle concurrently, one of the 24<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> 25flags must be specified with any non-cursor <a href="../../api_c/dbt_class.html">DBT</a> used for key or 26data retrieval.)</p> 27<p>When using the cursor Berkeley DB calls to retrieve key/data items under the 28C/C++ APIs (for example, <a href="../../api_c/dbc_get.html">DBcursor->get</a>), the memory to which the 29pointer stored into the <a href="../../api_c/dbt_class.html">DBT</a> refers is only valid until the next 30call 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> 31<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> 32</td></tr></table> 33<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 34</body> 35</html> 36
