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<title>Berkeley DB Reference Guide: Opening databases within the environment</title>
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<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Environment</dl></h3></td>
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<p>
<h1 align=center>Opening databases within the environment</h1>
<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_create.html">db_create</a> interface and specifying the appropriate environment
as an argument.
<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>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;
</pre></blockquote>
<p><blockquote><pre> /* 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);
return (ret);
}
<p>
/* Open database #1. */
if ((ret = db_create(&dbp1, dbenv, 0)) != 0) {
dbenv->err(dbenv, ret, "database create");
return (ret);
}
if ((ret = dbp1->open(dbp1,
NULL, DATABASE1, NULL, DB_BTREE, DB_CREATE, 0664)) != 0) {
dbenv->err(dbenv, ret, "DB->open: %s", DATABASE1);
return (ret);
}
<p>
/* Open database #2. */
if ((ret = db_create(&dbp2, dbenv, 0)) != 0) {
dbenv->err(dbenv, ret, "database create");
return (ret);
}
if ((ret = dbp2->open(dbp2,
NULL, DATABASE2, NULL, DB_HASH, DB_CREATE, 0664)) != 0) {
dbenv->err(dbenv, ret, "DB->open: %s", DATABASE2);
return (ret);
}
</pre></blockquote>
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