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<title>Berkeley DB: Db::close</title>
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<h1>Db::close</h1>
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<h3><pre>
#include <db_cxx.h>
<p>
int
Db::close(u_int32_t flags);
</pre></h3>
<h1>Description</h1>
<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. 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>The <b>flags</b> value must be set to 0 or by bitwise inclusively <b>OR</b>'ing together one or
more of the following values:
<p><dl compact>
<p><dt><a name="DB_NOSYNC">DB_NOSYNC</a><dd>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.
</dl>
<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>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>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.
<h1>Errors</h1>
<p>The Db::close method may fail and throw an exception or return a non-zero error for the following conditions:
<p><dl compact>
<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
</dl>
<p>The Db::close method may fail and throw an exception or return a non-zero error for errors specified for other Berkeley DB and C library or system methods.
If a catastrophic error has occurred, the Db::close method may fail and
either return <a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a> or throw a
<a href="../api_cxx/runrec_class.html">DbRunRecoveryException</a>,
in which case all subsequent Berkeley DB calls will fail in the same way.
<h1>Class</h1>
<a href="../api_cxx/db_class.html">Db</a>
<h1>See Also</h1>
<a href="../api_cxx/db_list.html">Databases and Related Methods</a>
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