1<!--$Id: mutex_set_max.so,v 10.5 2007/10/09 19:56:02 bostic Exp $--> 2<!--Copyright (c) 1997,2008 Oracle. All rights reserved.--> 3<!--See the file LICENSE for redistribution information.--> 4<html> 5<head> 6<title>Berkeley DB: DB_ENV->mutex_set_max</title> 7<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> 8<meta name="keywords" content="embedded,database,programmatic,toolkit,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,Java,C,C++"> 9</head> 10<body bgcolor=white> 11<table width="100%"><tr valign=top> 12<td> 13<b>DB_ENV->mutex_set_max</b> 14</td> 15<td align=right> 16<a href="/api_c/api_core.html"><img src="/images/api.gif" alt="API"></a> 17<a href="/ref/toc.html"><img src="/images/ref.gif" alt="Ref"></a></td> 18</tr></table> 19<hr size=1 noshade> 20<tt> 21<b><pre> 22#include <db.h> 23<p> 24int 25DB_ENV->mutex_set_max(DB_ENV *dbenv, u_int32_t max); 26<p> 27int 28DB_ENV->mutex_get_max(DB_ENV *dbenv, u_int32_t *maxp); 29<p> 30int 31DB_ENV->mutex_set_increment(DB_ENV *dbenv, u_int32_t increment); 32<p> 33int 34DB_ENV->mutex_get_increment(DB_ENV *dbenv, u_int32_t *incrementp); 35</pre></b> 36<hr size=1 noshade> 37<b>Description: DB_ENV->mutex_set_max</b> 38<p>Configure the total number of mutexes to allocate.</p> 39<p>Berkeley DB allocates a default number of mutexes based on the initial 40configuration of the database environment. That default calculation may 41be too small if the application has an unusual need for mutexes (for 42example, if the application opens an unexpectedly large number of 43databases) or too large (if the application is trying to minimize its 44memory footprint). The DB_ENV->mutex_set_max method is used to specify an 45absolute number of mutexes to allocate.</p> 46<p>Calling the DB_ENV->mutex_set_max method discards any value previously 47set using the DB_ENV->mutex_set_increment method.</p> 48<p>The database environment's total number of mutexes may also be configured using the 49environment's <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that 50file is a single line with the string "mutex_set_max", one or more whitespace 51characters, and the total number of mutexes. 52Because the <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment 53is opened, it will silently overrule configuration done before that 54time.</p> 55<p>The DB_ENV->mutex_set_max method configures a database environment, not only operations 56performed using the specified <a href="/api_c/env_class.html">DB_ENV</a> handle.</p> 57<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 58called. 59If the database environment already exists when 60<a href="/api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->mutex_set_max 61will be ignored. 62</p> 63<p>The DB_ENV->mutex_set_max method 64returns a non-zero error value on failure 65and 0 on success. 66</p> 67<b>Parameters</b> <br> 68 <b>max</b><ul compact><li>The <b>max</b> parameter is the absolute number of mutexes to 69allocate.</ul> 70<br> 71<br><b>Errors</b> 72<p>The DB_ENV->mutex_set_max method 73may fail and return one of the following non-zero errors:</p> 74<br> 75<b>EINVAL</b><ul compact><li>An 76invalid flag value or parameter was specified.</ul> 77<br> 78<hr size=1 noshade> 79<b>Description: DB_ENV->mutex_get_max</b> 80<p>The DB_ENV->mutex_get_max method returns the total number of mutexes allocated.</p> 81<p>The DB_ENV->mutex_get_max method may be called at any time during the life of the 82application.</p> 83<p>The DB_ENV->mutex_get_max method 84returns a non-zero error value on failure 85and 0 on success. 86</p> 87<b>Parameters</b> <br> 88 <b>maxp</b><ul compact><li>The DB_ENV->mutex_get_max method returns the 89total number of mutexes allocated in <b>maxp</b>.</ul> 90<br> 91<hr size=1 noshade> 92<b>Description: DB_ENV->mutex_set_increment</b> 93<p>Configure the number of additional mutexes to allocate.</p> 94<p>Additionally, an application may want to allocate mutexes for its own 95use. The DB_ENV->mutex_set_increment method is used to add a number of 96mutexes to the default allocation.</p> 97<p>Calling the DB_ENV->mutex_set_increment method discards any value previously 98set using the DB_ENV->mutex_set_max method.</p> 99<p>The database environment's number of additional mutexes may also be configured using the 100environment's <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that 101file is a single line with the string "mutex_set_increment", one or more whitespace 102characters, and the number of additional mutexes. 103Because the <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment 104is opened, it will silently overrule configuration done before that 105time.</p> 106<p>The DB_ENV->mutex_set_increment method configures a database environment, not only operations 107performed using the specified <a href="/api_c/env_class.html">DB_ENV</a> handle.</p> 108<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 109called. 110If the database environment already exists when 111<a href="/api_c/env_open.html">DB_ENV->open</a> is called, the information specified to DB_ENV->mutex_set_increment 112will be ignored. 113</p> 114<p>The DB_ENV->mutex_set_increment method 115returns a non-zero error value on failure 116and 0 on success. 117</p> 118<b>Parameters</b> <br> 119 <b>increment</b><ul compact><li>The <b>increment</b> parameter is the number of additional mutexes to 120allocate.</ul> 121<br> 122<br><b>Errors</b> 123<p>The DB_ENV->mutex_set_increment method 124may fail and return one of the following non-zero errors:</p> 125<br> 126<b>EINVAL</b><ul compact><li>An 127invalid flag value or parameter was specified.</ul> 128<br> 129<hr size=1 noshade> 130<b>Description: DB_ENV->mutex_get_increment</b> 131<p>The DB_ENV->mutex_get_increment method returns the number of additional mutexes to allocate.</p> 132<p>The DB_ENV->mutex_get_increment method may be called at any time during the life of the 133application.</p> 134<p>The DB_ENV->mutex_get_increment method 135returns a non-zero error value on failure 136and 0 on success. 137</p> 138<b>Parameters</b> <br> 139 <b>incrementp</b><ul compact><li>The DB_ENV->mutex_get_increment method returns the 140number of additional mutexes to allocate in <b>incrementp</b>.</ul> 141<br> 142<hr size=1 noshade> 143<br><b>Class</b> 144<a href="/api_c/env_class.html">DB_ENV</a> 145<br><b>See Also</b> 146<a href="/api_c/env_list.html">Database Environments and Related Methods</a> 147</tt> 148<table width="100%"><tr><td><br></td><td align=right> 149<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> 150</td></tr></table> 151<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 152</body> 153</html> 154
