<!--$Id: open.so,v 10.19 2003/10/18 19:16:01 bostic Exp $--> <!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> <!--See the file LICENSE for redistribution information.--> <html> <head> <title>Berkeley DB Reference Guide: Opening databases within the environment</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>Environment</dl></b></td> <td align=right><a href="../env/create.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../env/error.html"><img src="../../images/next.gif" alt="Next"></a> </td></tr></table> <p align=center><b>Opening databases within the environment</b></p> <p>Once the environment has been created, database handles may be created and then opened within the environment. This is done by calling the <a href="../../api_c/db_class.html">db_create</a> function and specifying the appropriate environment as an argument.</p> <p>File naming, database operations, and error handling will all be done as specified for the environment. For example, if the <a href="../../api_c/env_open.html#DB_INIT_LOCK">DB_INIT_LOCK</a> or <a href="../../api_c/env_open.html#DB_INIT_CDB">DB_INIT_CDB</a> flags were specified when the environment was created or joined, database operations will automatically perform all necessary locking operations for the application.</p> <p>The following is a simple example of opening two databases within a database environment:</p> <blockquote><pre> DB_ENV *dbenv; DB *dbp1, *dbp2; int ret; <p> dbenv = NULL; dbp1 = dbp2 = NULL; <p> /* * Create an environment and initialize it for additional error * reporting. */ if ((ret = db_env_create(&dbenv, 0)) != 0) { fprintf(errfp, "%s: %s\n", progname, db_strerror(ret)); return (ret); } <p> dbenv->set_errfile(dbenv, errfp); dbenv->set_errpfx(dbenv, progname); <p> /* Open an environment with just a memory pool. */ if ((ret = dbenv->open(dbenv, home, DB_CREATE | DB_INIT_MPOOL, 0)) != 0) { dbenv->err(dbenv, ret, "environment open: %s", home); goto err; } <p> /* Open database #1. */ if ((ret = db_create(&dbp1, dbenv, 0)) != 0) { dbenv->err(dbenv, ret, "database create"); goto err; } if ((ret = dbp1->open(dbp1, NULL, DATABASE1, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) { dbenv->err(dbenv, ret, "DB->open: %s", DATABASE1); goto err; } <p> /* Open database #2. */ if ((ret = db_create(&dbp2, dbenv, 0)) != 0) { dbenv->err(dbenv, ret, "database create"); goto err; } if ((ret = dbp2->open(dbp2, NULL, DATABASE2, NULL, DB_HASH, DB_CREATE, 0664)) != 0) { dbenv->err(dbenv, ret, "DB->open: %s", DATABASE2); goto err; } <p> return (0); <p> err: if (dbp2 != NULL) (void)dbp2->close(dbp2, 0); if (dbp1 != NULL) (void)dbp2->close(dbp1, 0); (void)dbenv->close(dbenv, 0); return (1); }</pre></blockquote> <table width="100%"><tr><td><br></td><td align=right><a href="../env/create.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../env/error.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>