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90 lines
4.6 KiB
HTML
<!--$Id: env_set_cachesize.so,v 10.19 2000/05/20 16:29:11 bostic Exp $-->
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<!--$Id: m4.cachesize,v 10.7 2000/02/11 18:54:45 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: DbEnv::set_cachesize</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>DbEnv::set_cachesize</h1>
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</td>
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<td width="1%">
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<a href="../api_cxx/cxx_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_cxx.h>
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<p>
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int
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DbEnv::set_cachesize(u_int32_t gbytes, u_int32_t bytes, int ncache);
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</pre></h3>
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<h1>Description</h1>
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<p>Set the size of the database's shared memory buffer pool, i.e., the cache,
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to <b>gbytes</b> gigabytes plus <b>bytes</b>. The cache should be the
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size of the normal working data set of the application, with some small
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amount of additional memory for unusual situations. (Note, the working
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set is not the same as the number of simultaneously referenced pages, and
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should be quite a bit larger!)
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<p>The default cache size is 256KB, and may not be specified as less than
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20KB. Any cache size less than 500MB is automatically increased by 25%
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to account for buffer pool overhead, cache sizes larger than 500MB are
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used as specified. For information on tuning the Berkeley DB cache size, see
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<a href="../ref/am_conf/cachesize.html">Selecting a cache size</a>.
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<p>It is possible to specify caches to Berkeley DB that are large enough so that
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they cannot be allocated contiguously on some architectures, e.g., some
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releases of Solaris limit the amount of memory that may be allocated
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contiguously by a process. If <b>ncache</b> is 0 or 1, the cache will
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be allocated contiguously in memory. If it is greater than 1, the cache
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will be broken up into <b>ncache</b> equally sized separate pieces of
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memory.
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<p>The DbEnv::set_cachesize interface may only be used to configure Berkeley DB before
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the <a href="../api_cxx/env_open.html">DbEnv::open</a> interface is called.
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<p>The DbEnv::set_cachesize method either returns a non-zero error value or throws an exception that
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encapsulates a non-zero error value on failure, and returns 0 on success.
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<p>The database environment's cache size may also be set using the environment's
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<b>DB_CONFIG</b> file. The syntax of the entry in that file is a
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single line with the string "set_cachesize", one or more whitespace characters,
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and the three arguments specified to this interface, separated by whitespace
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characters, for example, "set_cachesize 1 500 2". Because the <b>DB_CONFIG</b> file is read when the database
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environment is opened, it will silently overrule configuration done
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before that time.
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<h1>Errors</h1>
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<p><dl compact>
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<p><dt>EINVAL<dd>An invalid flag value or parameter was specified.
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<p>Called after <a href="../api_cxx/env_open.html">DbEnv::open</a> was called.
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<p>The specified cache size was impossibly small.
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</dl>
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<h3>Class</h3>
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<a href="../api_cxx/dbenv_class.html">DbEnv</a>
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<h1>See Also</h1>
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<a href="../api_cxx/env_close.html">DbEnv::close</a>,
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<a href="../api_cxx/env_open.html">DbEnv::open</a>,
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<a href="../api_cxx/env_remove.html">DbEnv::remove</a>,
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<a href="../api_cxx/db_err.html">DbEnv::err</a>,
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<a href="../api_cxx/env_strerror.html">DbEnv::strerror</a>,
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<a href="../api_cxx/env_version.html">DbEnv::version</a>,
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<a href="../api_cxx/env_set_cachesize.html">DbEnv::set_cachesize</a>,
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<a href="../api_cxx/env_set_errcall.html">DbEnv::set_errcall</a>,
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<a href="../api_cxx/env_set_errfile.html">DbEnv::set_errfile</a>,
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<a href="../api_cxx/env_set_error_stream.html">DbEnv::set_error_stream</a>,
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<a href="../api_cxx/env_set_errpfx.html">DbEnv::set_errpfx</a>,
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<a href="../api_cxx/env_set_flags.html">DbEnv::set_flags</a>,
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<a href="../api_cxx/env_set_mutexlocks.html">DbEnv::set_mutexlocks</a>,
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<a href="../api_cxx/env_set_paniccall.html">DbEnv::set_paniccall</a>,
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and
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<a href="../api_cxx/env_set_verbose.html">DbEnv::set_verbose</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_cxx/cxx_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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</body>
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