<!--$Id: open.so,v 11.11 2003/10/18 19:16:14 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB Reference Guide: Release 3.0: database open/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><dl><dt>Berkeley DB Reference Guide:<dd>Upgrading Berkeley DB Applications</dl></b></td> <td align=right><a href="../upgrade.3.0/dbenv.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../upgrade.3.0/xa.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p align=center><b>Release 3.0: database open/close</b></p> <p>Database opens were changed in the Berkeley DB 3.0 release in a similar way to environment opens.</p> <p>To upgrade your application, first find each place your application opens a database, that is, calls the db_open function. Each of these calls should be replaced with calls to <a href="../../api_c/db_class.html">db_create</a> and <a href="../../api_c/db_open.html">DB->open</a>.</p> <p>Here's an example creating a Berkeley DB database using the 2.X interface:</p> <blockquote><pre>DB *dbp; DB_ENV *dbenv; int ret; <p> if ((ret = db_open(DATABASE, DB_BTREE, DB_CREATE, 0664, dbenv, NULL, &dbp)) != 0) return (ret);</pre></blockquote> <p>In the Berkeley DB 3.0 release, this code would be written as:</p> <blockquote><pre>DB *dbp; DB_ENV *dbenv; int ret; <p> if ((ret = db_create(&dbp, dbenv, 0)) != 0) return (ret); <p> if ((ret = dbp->open(dbp, DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) { (void)dbp->close(dbp, 0); return (ret); }</pre></blockquote> <p>As you can see, the arguments to db_open and to <a href="../../api_c/db_open.html">DB->open</a> are largely the same. There is some re-organization, and note that the enclosing <a href="../../api_c/env_class.html">DB_ENV</a> structure is specified when the <a href="../../api_c/db_class.html">DB</a> object is created using the <a href="../../api_c/db_class.html">db_create</a> function. There is one additional argument to <a href="../../api_c/db_open.html">DB->open</a>, argument #3. For backward compatibility with the 2.X Berkeley DB releases, simply set that argument to NULL.</p> <p>There are two additional issues with the db_open call.</p> <p>First, it was possible in the 2.X releases for an application to provide an environment that did not contain a shared memory buffer pool as the database environment, and Berkeley DB would create a private one automatically. This functionality is no longer available, applications must specify the <a href="../../api_c/env_open.html#DB_INIT_MPOOL">DB_INIT_MPOOL</a> flag if databases are going to be opened in the environment.</p> <p>The final issue with upgrading the db_open call is that the DB_INFO structure is no longer used, having been replaced by individual methods on the <a href="../../api_c/db_class.html">DB</a> handle. That change is discussed in detail later in this chapter.</p> <table width="100%"><tr><td><br></td><td align=right><a href="../upgrade.3.0/dbenv.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../upgrade.3.0/xa.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> </body> </html>