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119 lines
6.5 KiB
HTML
<!--$Id: db_close.so,v 10.27 2000/09/08 15:20:28 bostic Exp $-->
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<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.-->
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<!--All rights reserved.-->
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<html>
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<head>
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<title>Berkeley DB: DB->close</title>
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<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit.">
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<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++">
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</head>
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<body bgcolor=white>
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<a name="2"><!--meow--></a>
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<table><tr valign=top>
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<td>
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<h1>DB->close</h1>
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</td>
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<td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<hr size=1 noshade>
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<tt>
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<h3><pre>
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#include <db.h>
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<p>
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int
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DB->close(DB *db, u_int32_t flags);
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</pre></h3>
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<h1>Description</h1>
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<p>The DB->close function flushes any cached database information to disk,
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closes any open cursors, frees any allocated resources, and closes any
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underlying files. Since key/data pairs are cached in memory, failing to
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sync the file with the DB->close or <a href="../api_c/db_sync.html">DB->sync</a> function may result
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in inconsistent or lost information.
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<p>The <b>flags</b> parameter must be set to 0 or the following value:
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<p><dl compact>
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<p><dt><a name="DB_NOSYNC">DB_NOSYNC</a><dd>Do not flush cached information to disk.
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<p>The <a href="../api_c/db_close.html#DB_NOSYNC">DB_NOSYNC</a> flag is a dangerous option. It should only be set
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if the application is doing logging (with transactions) so that the
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database is recoverable after a system or application crash, or if the
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database is always generated from scratch after any system or application
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crash.
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<p><b>It is important to understand that flushing cached information to disk
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only minimizes the window of opportunity for corrupted data.</b>
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While unlikely, it is possible for database corruption to happen if a
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system or application crash occurs while writing data to the database.
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To ensure that database corruption never occurs, applications must either:
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use transactions and logging with automatic recovery, use logging and
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application-specific recovery, or edit a copy of the database,
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and, once all applications using the database have successfully called
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DB->close, atomically replace the original database with the
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updated copy.
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</dl>
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<p>When multiple threads are using the Berkeley DB handle concurrently, only a single
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thread may call the DB->close function.
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<p>Once DB->close has been called, regardless of its return, the
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DB handle may not be accessed again.
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<a name="3"><!--meow--></a>
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<p>The DB->close function returns a non-zero error value on failure, 0 on success, and returns <a href="../api_c/memp_fsync.html#DB_INCOMPLETE">DB_INCOMPLETE</a> if the underlying database still has
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dirty pages in the cache. (The only reason to return
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<a href="../api_c/memp_fsync.html#DB_INCOMPLETE">DB_INCOMPLETE</a> is if another thread of control was writing pages
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in the underlying database file at the same time as the
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DB->close function was called. For this reason, a return of
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<a href="../api_c/memp_fsync.html#DB_INCOMPLETE">DB_INCOMPLETE</a> can normally be ignored, or, in cases where it is
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a possible return value, the <a href="../api_c/db_close.html#DB_NOSYNC">DB_NOSYNC</a> option should probably
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have been specified.)
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<p>The DB->close function returns a non-zero error value on failure and 0 on success.
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<h1>Errors</h1>
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<p>The DB->close function may fail and return a non-zero error for errors specified for other Berkeley DB and C library or system functions.
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If a catastrophic error has occurred, the DB->close function may fail and return
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<a href="../ref/program/errorret.html#DB_RUNRECOVERY">DB_RUNRECOVERY</a>, in which case all subsequent Berkeley DB calls will fail
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in the same way.
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<h1>See Also</h1>
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<a href="../api_c/db_create.html">db_create</a>,
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<a href="../api_c/db_close.html">DB->close</a>,
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<a href="../api_c/db_cursor.html">DB->cursor</a>,
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<a href="../api_c/db_del.html">DB->del</a>,
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<a href="../api_c/db_err.html">DB->err</a>,
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<a href="../api_c/db_fd.html">DB->fd</a>,
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<a href="../api_c/db_get.html">DB->get</a>,
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<a href="../api_c/db_get_byteswapped.html">DB->get_byteswapped</a>,
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<a href="../api_c/db_get_type.html">DB->get_type</a>,
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<a href="../api_c/db_join.html">DB->join</a>,
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<a href="../api_c/db_key_range.html">DB->key_range</a>,
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<a href="../api_c/db_open.html">DB->open</a>,
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<a href="../api_c/db_put.html">DB->put</a>,
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<a href="../api_c/db_remove.html">DB->remove</a>,
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<a href="../api_c/db_set_bt_compare.html">DB->set_bt_compare</a>,
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<a href="../api_c/db_set_bt_minkey.html">DB->set_bt_minkey</a>,
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<a href="../api_c/db_set_bt_prefix.html">DB->set_bt_prefix</a>,
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<a href="../api_c/db_set_cachesize.html">DB->set_cachesize</a>,
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<a href="../api_c/db_set_dup_compare.html">DB->set_dup_compare</a>,
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<a href="../api_c/db_set_errcall.html">DB->set_errcall</a>,
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<a href="../api_c/db_set_errfile.html">DB->set_errfile</a>,
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<a href="../api_c/db_set_errpfx.html">DB->set_errpfx</a>,
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<a href="../api_c/db_set_flags.html">DB->set_flags</a>,
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<a href="../api_c/db_set_h_ffactor.html">DB->set_h_ffactor</a>,
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<a href="../api_c/db_set_h_hash.html">DB->set_h_hash</a>,
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<a href="../api_c/db_set_h_nelem.html">DB->set_h_nelem</a>,
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<a href="../api_c/db_set_lorder.html">DB->set_lorder</a>,
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<a href="../api_c/db_set_malloc.html">DB->set_malloc</a>,
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<a href="../api_c/db_set_pagesize.html">DB->set_pagesize</a>,
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<a href="../api_c/db_set_paniccall.html">DB->set_paniccall</a>,
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<a href="../api_c/db_set_q_extentsize.html">DB->set_q_extentsize</a>,
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<a href="../api_c/db_set_realloc.html">DB->set_realloc</a>,
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<a href="../api_c/db_set_re_delim.html">DB->set_re_delim</a>,
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<a href="../api_c/db_set_re_len.html">DB->set_re_len</a>,
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<a href="../api_c/db_set_re_pad.html">DB->set_re_pad</a>,
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<a href="../api_c/db_set_re_source.html">DB->set_re_source</a>,
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<a href="../api_c/db_stat.html">DB->stat</a>,
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<a href="../api_c/db_sync.html">DB->sync</a>,
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<a href="../api_c/db_upgrade.html">DB->upgrade</a>
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and
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<a href="../api_c/db_verify.html">DB->verify</a>.
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</tt>
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<table><tr><td><br></td><td width="1%">
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<a href="../api_c/c_index.html"><img src="../images/api.gif" alt="API"></a><a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a>
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</td></tr></table>
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<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font>
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