<!--$Id: db_close.so,v 10.55 2004/08/13 03:38:55 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB: Db::close</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> <table width="100%"><tr valign=top> <td> <b>Db::close</b> </td> <td align=right> <a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a> <a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td> </tr></table> <hr size=1 noshade> <tt> <b><pre> #include <db_cxx.h> <p> int Db::close(u_int32_t flags); </pre></b> <hr size=1 noshade> <b>Description: Db::close</b> <p>The Db::close method flushes any cached database information to disk, closes any open cursors, frees any allocated resources, and closes any underlying files.</p> <p>The <a href="../api_cxx/db_class.html">Db</a> handle should not be closed while any other handle that refers to it is not yet closed; for example, database handles must not be closed while cursor handles into the database remain open, or transactions that include operations on the database have not yet been committed or aborted. Specifically, this includes <a href="../api_cxx/dbc_class.html">Dbc</a> and <a href="../api_cxx/txn_class.html">DbTxn</a> handles.</p> <p>Because key/data pairs are cached in memory, failing to sync the file with the Db::close or <a href="../api_cxx/db_sync.html">Db::sync</a> method may result in inconsistent or lost information.</p> <p>When called on a database that is the primary database for a secondary index, the primary database should be closed only after all secondary indices which reference it have been closed.</p> <p>When multiple threads are using the <a href="../api_cxx/db_class.html">Db</a> concurrently, only a single thread may call the Db::close method.</p> <p>The <a href="../api_cxx/db_class.html">Db</a> handle may not be accessed again after Db::close is called, regardless of its return.</p> <p>The Db::close method either returns a non-zero error value or throws an exception that encapsulates a non-zero error value on failure, and returns 0 on success. </p> <b>Parameters</b> <br> <b>flags</b><ul compact><li>The <b>flags</b> parameter must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one or more of the following values: <br> <b><a name="DB_NOSYNC">DB_NOSYNC</a></b><ul compact><li>Do not flush cached information to disk. The <a href="../api_cxx/db_close.html#DB_NOSYNC">DB_NOSYNC</a> flag is a dangerous option. It should be set only if the application is doing logging (with transactions) so that the database is recoverable after a system or application crash, or if the database is always generated from scratch after any system or application crash. <p><b>It is important to understand that flushing cached information to disk only minimizes the window of opportunity for corrupted data.</b> Although unlikely, it is possible for database corruption to happen if a system or application crash occurs while writing data to the database. To ensure that database corruption never occurs, applications must either: use transactions and logging with automatic recovery; use logging and application-specific recovery; or edit a copy of the database, and once all applications using the database have successfully called Db::close, atomically replace the original database with the updated copy.</p></ul> <br></ul> <br> <br><b>Errors</b> <p>The Db::close method may fail and throw <a href="../api_cxx/except_class.html">DbException</a>, encapsulating one of the following non-zero errors, or return one of the following non-zero errors:</p> <br> <b>EINVAL</b><ul compact><li>An invalid flag value or parameter was specified.</ul> <br> <hr size=1 noshade> <br><b>Class</b> <a href="../api_cxx/db_class.html">Db</a> <br><b>See Also</b> <a href="../api_cxx/db_list.html">Databases and Related Methods</a> </tt> <table width="100%"><tr><td><br></td><td align=right> <a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>