Import BSDDB 4.7.25 (as of svn r89086)
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Zachary Ware
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docs/api_c/mutex_set_max.html
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docs/api_c/mutex_set_max.html
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<!--$Id: mutex_set_max.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: DB_ENV->mutex_set_max</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>DB_ENV->mutex_set_max</b>
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</td>
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<td align=right>
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<a href="../api_c/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.h>
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<p>
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int
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DB_ENV->mutex_set_max(DB_ENV *dbenv, u_int32_t max);
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<p>
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int
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DB_ENV->mutex_get_max(DB_ENV *dbenv, u_int32_t *maxp);
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<p>
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int
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DB_ENV->mutex_set_increment(DB_ENV *dbenv, u_int32_t increment);
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<p>
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int
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DB_ENV->mutex_get_increment(DB_ENV *dbenv, u_int32_t *incrementp);
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</pre></b>
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<hr size=1 noshade>
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<b>Description: DB_ENV->mutex_set_max</b>
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<p>Configure the total number of mutexes to allocate.</p>
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<p>Berkeley DB allocates a default number of mutexes based on the initial
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configuration of the database environment. That default calculation may
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be too small if the application has an unusual need for mutexes (for
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example, if the application opens an unexpectedly large number of
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databases) or too large (if the application is trying to minimize its
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memory footprint). The DB_ENV->mutex_set_max method is used to specify an
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absolute number of mutexes to allocate.</p>
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<p>Calling the DB_ENV->mutex_set_max method discards any value previously
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set using the DB_ENV->mutex_set_increment method.</p>
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<p>The database environment's total number of mutexes may also be configured using the
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environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that
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file is a single line with the string "mutex_set_max", one or more whitespace
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characters, and the total number of mutexes.
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Because the <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment
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is opened, it will silently overrule configuration done before that
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time.</p>
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<p>The DB_ENV->mutex_set_max method configures a database environment, not only operations
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performed using the specified <a href="../api_c/env_class.html">DB_ENV</a> handle.</p>
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<p>The DB_ENV->mutex_set_max method may not be called after the <a href="../api_c/env_open.html">DB_ENV->open</a> method is
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called.
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If the database environment already exists when
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<a href="../api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->mutex_set_max
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will be ignored.
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</p>
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<p>The DB_ENV->mutex_set_max method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>max</b><ul compact><li>The <b>max</b> parameter is the absolute number of mutexes to
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allocate.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DB_ENV->mutex_set_max method
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may fail and return one of the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>An
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<b>Description: DB_ENV->mutex_get_max</b>
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<p>The DB_ENV->mutex_get_max method returns the total number of mutexes allocated.</p>
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<p>The DB_ENV->mutex_get_max method may be called at any time during the life of the
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application.</p>
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<p>The DB_ENV->mutex_get_max method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>maxp</b><ul compact><li>The DB_ENV->mutex_get_max method returns the
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total number of mutexes allocated in <b>maxp</b>.</ul>
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<br>
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<hr size=1 noshade>
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<b>Description: DB_ENV->mutex_set_increment</b>
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<p>Configure the number of additional mutexes to allocate.</p>
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<p>Additionally, an application may want to allocate mutexes for its own
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use. The DB_ENV->mutex_set_increment method is used to add a number of
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mutexes to the default allocation.</p>
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<p>Calling the DB_ENV->mutex_set_increment method discards any value previously
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set using the DB_ENV->mutex_set_max method.</p>
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<p>The database environment's number of additional mutexes may also be configured using the
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environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that
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file is a single line with the string "mutex_set_increment", one or more whitespace
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characters, and the number of additional mutexes.
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Because the <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment
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is opened, it will silently overrule configuration done before that
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time.</p>
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<p>The DB_ENV->mutex_set_increment method configures a database environment, not only operations
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performed using the specified <a href="../api_c/env_class.html">DB_ENV</a> handle.</p>
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<p>The DB_ENV->mutex_set_increment method may not be called after the <a href="../api_c/env_open.html">DB_ENV->open</a> method is
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called.
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If the database environment already exists when
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<a href="../api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->mutex_set_increment
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will be ignored.
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</p>
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<p>The DB_ENV->mutex_set_increment method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>increment</b><ul compact><li>The <b>increment</b> parameter is the number of additional mutexes to
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allocate.</ul>
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<br>
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<br><b>Errors</b>
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<p>The DB_ENV->mutex_set_increment method
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may fail and return one of the following non-zero errors:</p>
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<br>
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<b>EINVAL</b><ul compact><li>An
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invalid flag value or parameter was specified.</ul>
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<br>
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<hr size=1 noshade>
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<b>Description: DB_ENV->mutex_get_increment</b>
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<p>The DB_ENV->mutex_get_increment method returns the number of additional mutexes to allocate.</p>
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<p>The DB_ENV->mutex_get_increment method may be called at any time during the life of the
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application.</p>
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<p>The DB_ENV->mutex_get_increment method
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returns a non-zero error value on failure
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and 0 on success.
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</p>
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<b>Parameters</b> <br>
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<b>incrementp</b><ul compact><li>The DB_ENV->mutex_get_increment method returns the
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number of additional mutexes to allocate in <b>incrementp</b>.</ul>
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<br>
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<hr size=1 noshade>
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<br><b>Class</b>
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<a href="../api_c/env_class.html">DB_ENV</a>
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<br><b>See Also</b>
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<a href="../api_c/env_list.html">Database Environments 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_c/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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