1<!--$Id: sync.so,v 10.18 2003/10/18 19:15:53 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: Flushing the database cache</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>
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/verify.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../am/close.html"><img src="../../images/next.gif" alt="Next"></a>
15</td></tr></table>
16<p align=center><b>Flushing the database cache</b></p>
17<p>The <a href="../../api_c/db_sync.html">DB-&gt;sync</a> method flushes all modified records from the database
18cache to disk.</p>
19<p><b>It is important to understand that flushing cached information
20to disk only minimizes the window of opportunity for corrupted data, it
21does not eliminate the possibility.</b></p>
22<p>While unlikely, it is possible for database corruption to happen if a
23system or application crash occurs while writing data to the database. To
24ensure that database corruption never occurs, applications must either:</p>
25<p><ul type=disc>
26<li>Use transactions and logging with automatic recovery.
27<li>Use logging and application-specific recovery.
28<li>Edit a copy of the database, and, once all applications
29using the database have successfully called <a href="../../api_c/db_close.html">DB-&gt;close</a>, use
30system operations (for example, the POSIX rename system call) to
31atomically replace the original database with the updated copy.
32</ul>
33<table width="100%"><tr><td><br></td><td align=right><a href="../am/verify.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../am/close.html"><img src="../../images/next.gif" alt="Next"></a>
34</td></tr></table>
35<p><font size=1>Copyright (c) 1996,2008 Oracle.  All rights reserved.</font>
36</body>
37</html>
38