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diff --git a/docs/programmer_reference/mp.html b/docs/programmer_reference/mp.html index 02e23090..12b2649c 100644 --- a/docs/programmer_reference/mp.html +++ b/docs/programmer_reference/mp.html @@ -14,13 +14,11 @@ <body> <div xmlns="" class="navheader"> <div class="libver"> - <p>Library Version 11.2.5.3</p> + <p>Library Version 12.1.6.1</p> </div> <table width="100%" summary="Navigation header"> <tr> - <th colspan="3" align="center">Chapter 18. - The Memory Pool Subsystem - </th> + <th colspan="3" align="center">Chapter 18. The Memory Pool Subsystem </th> </tr> <tr> <td width="20%" align="left"><a accesskey="p" href="log_limits.html">Prev</a> </td> @@ -34,9 +32,7 @@ <div class="titlepage"> <div> <div> - <h2 class="title"><a id="mp"></a>Chapter 18. - The Memory Pool Subsystem - </h2> + <h2 class="title"><a id="mp"></a>Chapter 18. The Memory Pool Subsystem </h2> </div> </div> </div> @@ -79,64 +75,110 @@ </div> </div> </div> - <p>The Memory Pool subsystem is the general-purpose shared memory buffer -pool used by Berkeley DB. This module is useful outside of the Berkeley DB package -for processes that require page-oriented, shared and cached file -access. (However, such "use outside of Berkeley DB" is not supported -in replicated environments.)</p> - <p>A <span class="emphasis"><em>memory pool</em></span> is a memory cache shared among any number of -threads of control. The <a href="../api_reference/C/envopen.html#envopen_DB_INIT_MPOOL" class="olink">DB_INIT_MPOOL</a> flag to the -<a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a> method opens and optionally creates a memory pool. When -that pool is no longer in use, it should be closed using the -<a href="../api_reference/C/envclose.html" class="olink">DB_ENV->close()</a> method.</p> - <p>The <a href="../api_reference/C/mempfcreate.html" class="olink">DB_ENV->memp_fcreate()</a> method returns a <a href="../api_reference/C/memp.html" class="olink">DB_MPOOLFILE</a> handle on an -underlying file within the memory pool. The file may be opened using -the <a href="../api_reference/C/mempfopen.html" class="olink">DB_MPOOLFILE->open()</a> method. The <a href="../api_reference/C/mempfget.html" class="olink">DB_MPOOLFILE->get()</a> method is used to retrieve -pages from files in the pool. All retrieved pages must be subsequently -returned using the <a href="../api_reference/C/mempput.html" class="olink">DB_MPOOLFILE->put()</a> method. At the time pages are returned, -they may be marked <span class="bold"><strong>dirty</strong></span>, which causes them to be written to -the underlying file before being discarded from the pool. If there is -insufficient room to bring a new page in the pool, a page is selected -to be discarded from the pool using a least-recently-used algorithm. -All dirty pages in the pool from the file may be flushed using the -<a href="../api_reference/C/mempfsync.html" class="olink">DB_MPOOLFILE->sync()</a> method. When the file handle is no longer in use, it -should be closed using the <a href="../api_reference/C/mempfclose.html" class="olink">DB_MPOOLFILE->close()</a> method.</p> - <p>There are additional configuration interfaces that apply when opening -a new file in the memory pool:</p> + <p> + The Memory Pool subsystem is the general-purpose shared + memory buffer pool used by Berkeley DB. This module is useful + outside of the Berkeley DB package for processes that require + page-oriented, shared and cached file access. (However, such + "use outside of Berkeley DB" is not supported in replicated + environments.) + </p> + <p> + A <span class="emphasis"><em>memory pool</em></span> is a memory cache shared + among any number of threads of control. The <a href="../api_reference/C/envopen.html#envopen_DB_INIT_MPOOL" class="olink">DB_INIT_MPOOL</a> + flag to the <a href="../api_reference/C/envopen.html" class="olink">DB_ENV->open()</a> method opens and optionally creates a + memory pool. When that pool is no longer in use, it should be + closed using the <a href="../api_reference/C/envclose.html" class="olink">DB_ENV->close()</a> method. + </p> + <p> + The <a href="../api_reference/C/mempfcreate.html" class="olink">DB_ENV->memp_fcreate()</a> method returns a <a href="../api_reference/C/memp.html" class="olink">DB_MPOOLFILE</a> handle on an + underlying file within the memory pool. The file may be opened + using the <a href="../api_reference/C/mempfopen.html" class="olink">DB_MPOOLFILE->open()</a> method. The <a href="../api_reference/C/mempfget.html" class="olink">DB_MPOOLFILE->get()</a> method is used to + retrieve pages from files in the pool. All retrieved pages + must be subsequently returned using the <a href="../api_reference/C/mempput.html" class="olink">DB_MPOOLFILE->put()</a> method. At + the time pages are returned, they may be marked <span class="bold"><strong>dirty</strong></span>, which causes them to be + written to the underlying file before being discarded from the + pool. If there is insufficient room to bring a new page in the + pool, a page is selected to be discarded from the pool using a + least-recently-used algorithm. All dirty pages in the pool + from the file may be flushed using the <a href="../api_reference/C/mempfsync.html" class="olink">DB_MPOOLFILE->sync()</a> method. + When the file handle is no longer in use, it should be closed + using the <a href="../api_reference/C/mempfclose.html" class="olink">DB_MPOOLFILE->close()</a> method. + </p> + <p> + There are additional configuration interfaces that apply + when opening a new file in the memory pool: + </p> <div class="itemizedlist"> <ul type="disc"> - <li>The <a href="../api_reference/C/mempset_clear_len.html" class="olink">DB_MPOOLFILE->set_clear_len()</a> method specifies the number of bytes to clear -when creating a new page in the memory pool.</li> - <li>The <a href="../api_reference/C/mempset_fileid.html" class="olink">DB_MPOOLFILE->set_fileid()</a> method specifies a unique ID associated with the file.</li> - <li>The <a href="../api_reference/C/mempset_ftype.html" class="olink">DB_MPOOLFILE->set_ftype()</a> method specifies the type of file for the purposes of -page input and output processing.</li> - <li>The <a href="../api_reference/C/mempset_lsn_offset.html" class="olink">DB_MPOOLFILE->set_lsn_offset()</a> method specifies the byte offset of each page's -log sequence number (<a href="../api_reference/C/lsn.html" class="olink">DB_LSN</a>) for the purposes of transaction -checkpoints.</li> - <li>The <a href="../api_reference/C/mempset_pgcookie.html" class="olink">DB_MPOOLFILE->set_pgcookie()</a> method specifies an application provided argument -for the purposes of page input and output processing.</li> + <li> + The <a href="../api_reference/C/mempset_clear_len.html" class="olink">DB_MPOOLFILE->set_clear_len()</a> method specifies the number + of bytes to clear when creating a new page in the memory + pool. + </li> + <li> + The <a href="../api_reference/C/mempset_fileid.html" class="olink">DB_MPOOLFILE->set_fileid()</a> method specifies a unique ID + associated with the file. + </li> + <li> + The <a href="../api_reference/C/mempset_ftype.html" class="olink">DB_MPOOLFILE->set_ftype()</a> method specifies the type of + file for the purposes of page input and output + processing. + </li> + <li> + The <a href="../api_reference/C/mempset_lsn_offset.html" class="olink">DB_MPOOLFILE->set_lsn_offset()</a> method specifies the byte + offset of each page's log sequence number (<a href="../api_reference/C/lsn.html" class="olink">DB_LSN</a>) for the + purposes of transaction checkpoints. + </li> + <li> + The <a href="../api_reference/C/mempset_pgcookie.html" class="olink">DB_MPOOLFILE->set_pgcookie()</a> method specifies an + application provided argument for the purposes of page + input and output processing. + </li> </ul> </div> - <p>There are additional interfaces for the memory pool as a whole:</p> + <p> + There are additional interfaces for the memory pool as a + whole: + </p> <div class="itemizedlist"> <ul type="disc"> - <li>It is possible to gradually flush buffers from the pool in order to -maintain a consistent percentage of clean buffers in the pool using -the <a href="../api_reference/C/memptrickle.html" class="olink">DB_ENV->memp_trickle()</a> method.</li> - <li>Because special-purpose processing may be necessary when pages are read -or written (for example, endian conversion, or page checksums), the -<a href="../api_reference/C/mempregister.html" class="olink">DB_ENV->memp_register()</a> function allows applications to specify automatic -input and output processing in these cases.</li> - <li>The <a href="../api_reference/C/db_stat.html" class="olink">db_stat</a> utility uses the <a href="../api_reference/C/mempstat.html" class="olink">DB_ENV->memp_stat()</a> method to display -statistics about the efficiency of the pool.</li> - <li>All dirty pages in the pool may be flushed using the <a href="../api_reference/C/mempsync.html" class="olink">DB_ENV->memp_sync()</a> method. -In addition, <a href="../api_reference/C/mempsync.html" class="olink">DB_ENV->memp_sync()</a> takes an argument that is specific to -database systems, and which allows the memory pool to be flushed up to -a specified log sequence number (<a href="../api_reference/C/lsn.html" class="olink">DB_LSN</a>).</li> - <li>The entire pool may be discarded using the <a href="../api_reference/C/envremove.html" class="olink">DB_ENV->remove()</a> method.</li> + <li> + It is possible to gradually flush buffers from the + pool in order to maintain a consistent percentage of clean + buffers in the pool using the <a href="../api_reference/C/memptrickle.html" class="olink">DB_ENV->memp_trickle()</a> + method. + </li> + <li> + Because special-purpose processing may be necessary + when pages are read or written (for example, endian + conversion, or page checksums), the <a href="../api_reference/C/mempregister.html" class="olink">DB_ENV->memp_register()</a> + function allows applications to specify automatic input + and output processing in these cases. + </li> + <li> + The <a href="../api_reference/C/db_stat.html" class="olink">db_stat</a> utility uses the <a href="../api_reference/C/mempstat.html" class="olink">DB_ENV->memp_stat()</a> method to display + statistics about the efficiency of the pool. + </li> + <li> + All dirty pages in the pool may be flushed using the + <a href="../api_reference/C/mempsync.html" class="olink">DB_ENV->memp_sync()</a> method. In addition, <a href="../api_reference/C/mempsync.html" class="olink">DB_ENV->memp_sync()</a> takes an + argument that is specific to database systems, and which + allows the memory pool to be flushed up to a specified log + sequence number (<a href="../api_reference/C/lsn.html" class="olink">DB_LSN</a>). + </li> + <li> + The entire pool may be discarded using the + <a href="../api_reference/C/envremove.html" class="olink">DB_ENV->remove()</a> method. + </li> </ul> </div> - <p>For more information on the memory pool subsystem methods, see the <a href="../api_reference/C/memp.html#memplist" class="olink">Memory Pools and Related Methods</a> section in the <em class="citetitle">Berkeley DB C API Reference Guide.</em> </p> + <p> + For more information on the memory pool subsystem methods, + see the <a href="../api_reference/C/memp.html#memplist" class="olink">Memory + Pools and Related Methods</a> section in the + <em class="citetitle">Berkeley DB C API Reference Guide.</em> + </p> </div> </div> <div class="navfooter"> |