72 lines
3.3 KiB
HTML
72 lines
3.3 KiB
HTML
<!--$Id: mempfile_class.html 63573 2008-05-23 21:43:21Z trent.nelson $-->
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<!--Copyright (c) 1997,2008 Oracle. All rights reserved.-->
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<!--See the file LICENSE for redistribution information.-->
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<html>
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<head>
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<title>Berkeley DB: DbMpoolFile</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,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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<table width="100%"><tr valign=top>
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<td>
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<b>DbMpoolFile</b>
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</td>
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<td align=right>
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<a href="../api_cxx/api_core.html"><img src="../images/api.gif" alt="API"></a>
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<a href="../ref/toc.html"><img src="../images/ref.gif" alt="Ref"></a></td>
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</tr></table>
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<hr size=1 noshade>
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<tt>
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<b><pre>
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#include <db_cxx.h>
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<p>
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class DbMpoolFile {
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public:
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DB_MPOOLFILE *DbMpoolFile::get_DB_MPOOLFILE();
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const DB_MPOOLFILE *DbMpoolFile::get_const_DB_MPOOLFILE() const;
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...
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};
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DbMpoolFile</b>
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<p>The memory pool interfaces for the Berkeley DB database environment are
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methods of the <a href="../api_cxx/env_class.html">DbEnv</a> handle. The <a href="../api_cxx/env_class.html">DbEnv</a> memory pool
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methods and the DbMpoolFile class provide general-purpose,
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page-oriented buffer management of files. Although designed to work
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with the other <a href="../api_cxx/db_class.html">Db</a> classes, they are also useful for more general
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purposes. The memory pools are referred to in this document as simply
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<i>pools</i>.</p>
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<p>Pools may be shared between processes. Pools are usually filled by
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pages from one or more files. Pages in the pool are replaced in LRU
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(least-recently-used) order, with each new page replacing the page that
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has been unused the longest. Pages retrieved from the pool using
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<a href="../api_cxx/memp_fget.html">DbMpoolFile::get</a> are <i>pinned</i> in the pool until they are
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returned to the control of the buffer pool using the <a href="../api_cxx/memp_fput.html">DbMpoolFile::put</a>
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method.</p>
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<p>The DbMpoolFile object is the handle for a file in the memory
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pool. The handle is not free-threaded. Once the <a href="../api_cxx/memp_fclose.html">DbMpoolFile::close</a> method
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is called, the handle may not be accessed again, regardless of that
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method's return.</p>
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<p>Each DbMpoolFile object has an associated DB_MPOOLFILE
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structure, which is used by the underlying implementation of Berkeley DB and
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its C-language API. The DbMpoolFile::get_DB_MPOOLFILE method returns a
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pointer to this struct. Given a const DbMpoolFile object,
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DbMpoolFile::get_const_DB_MPOOLFILE returns a const pointer to the same
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struct.</p>
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<p>These methods may be useful for Berkeley DB applications including both C
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and C++ language software. It should not be necessary to use these
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calls in a purely C++ application.</p>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_cxx/env_class.html">DbEnv</a>, DbMpoolFile
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<br><b>See Also</b>
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<a href="../api_cxx/memp_list.html">Memory Pools and Related Methods</a>
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</tt>
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<table width="100%"><tr><td><br></td><td align=right>
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<a href="../api_cxx/api_core.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>Copyright (c) 1996,2008 Oracle. All rights reserved.</font>
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</body>
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</html>
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