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<title>Berkeley DB Reference Guide: Release 3.0: database open/close</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<table width="100%"><tr valign=top>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Upgrading Berkeley DB Applications</dl></h3></td>
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<td align=right><a href="../../ref/upgrade.3.0/dbenv.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../reftoc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/upgrade.3.0/xa.html"><img src="../../images/next.gif" alt="Next"></a>
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<h1 align=center>Release 3.0: database open/close</h1>
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<p>Database opens were changed in the Berkeley DB 3.0 release in a similar way to
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<p>To upgrade your application, first find each place your application opens
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a database, that is, calls the db_open function. Each of these calls
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should be replaced with calls to <a href="../../api_c/db_create.html">db_create</a> and <a href="../../api_c/db_open.html">DB->open</a>.
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<p>Here's an example creating a Berkeley DB database using the 2.X interface:
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<p><blockquote><pre>DB *dbp;
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if ((ret = db_open(DATABASE,
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DB_BTREE, DB_CREATE, 0664, dbenv, NULL, &dbp)) != 0)
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return (ret);</pre></blockquote>
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<p>In the Berkeley DB 3.0 release, this code would be written as:
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<p><blockquote><pre>DB *dbp;
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if ((ret = db_create(&dbp, dbenv, 0)) != 0)
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if ((ret = dbp->open(dbp,
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DATABASE, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
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(void)dbp->close(dbp, 0);
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<p>As you can see, the arguments to db_open and to <a href="../../api_c/db_open.html">DB->open</a> are
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largely the same. There is some re-organization, and note that the
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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
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is created using the <a href="../../api_c/db_create.html">db_create</a> interface. There is one
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additional argument to <a href="../../api_c/db_open.html">DB->open</a>, argument #3. For backward
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compatibility with the 2.X Berkeley DB releases, simply set that argument to
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<p>There are two additional issues with the db_open call.
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<p>First, it was possible in the 2.X releases for an application to provide
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an environment that did not contain a shared memory buffer pool as the
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database environment, and Berkeley DB would create a private one automatically.
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This functionality is no longer available, applications must specify the
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<a href="../../api_c/env_open.html#DB_INIT_MPOOL">DB_INIT_MPOOL</a> flag if databases are going to be opened in the
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<p>The final issue with upgrading the db_open call is that the DB_INFO
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structure is no longer used, having been replaced by individual methods
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on the <a href="../../api_c/db_class.html">DB</a> handle. That change is discussed in detail later in
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