1<!--$Id: memp_maxwrite.so,v 10.6 2007/11/08 16:28:12 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: DbEnv::set_mp_max_write</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>DbEnv::set_mp_max_write</b> 14</td> 15<td align=right> 16<a href="/api_cxx/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_cxx.h> 23<p> 24int 25DbEnv::set_mp_max_write(int maxwrite, db_timeout_t maxwrite_sleep); 26<p> 27int 28DbEnv::get_mp_max_write(int *maxwritep, db_timeout_t *maxwrite_sleepp); 29</pre></b> 30<hr size=1 noshade> 31<b>Description: DbEnv::set_mp_max_write</b> 32<p>The DbEnv::set_mp_max_write method limits the number of sequential write 33operations scheduled by the library when flushing dirty pages from the 34cache.</p> 35<p>The database environment's maximum number of sequential write operations may also be configured using the 36environment's <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that 37file is a single line with the string "set_mp_max_write", one or more whitespace 38characters, and the maximum number of sequential writes and the number of microseconds 39to sleep, also separated by whitespace characters. 40Because the <a href="/ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment 41is opened, it will silently overrule configuration done before that 42time.</p> 43<p>The DbEnv::set_mp_max_write method configures a database environment, not only operations 44performed using the specified <a href="/api_cxx/env_class.html">DbEnv</a> handle.</p> 45<p>The DbEnv::set_mp_max_write method 46either returns a non-zero error value 47or throws an exception that encapsulates a non-zero error value on 48failure, and returns 0 on success. 49</p> 50<b>Parameters</b> <br> 51 <b>maxwrite</b><ul compact><li>The maximum number of sequential write operations scheduled by the 52library when flushing dirty pages from the cache, or 0 if there is 53no limitation on the number of sequential write operations.</ul> 54 <b>maxwrite_sleep</b><ul compact><li>The number of microseconds the thread of control should pause before 55scheduling further write operations. It must be specified as an 56unsigned 32-bit number of microseconds, limiting the maximum pause to 57roughly 71 minutes.</ul> 58<br> 59<br><b>Errors</b> 60<p>The DbEnv::set_mp_max_write method 61may fail and throw 62<a href="/api_cxx/except_class.html">DbException</a>, 63encapsulating one of the following non-zero errors, or return one of 64the following non-zero errors:</p> 65<br> 66<b>EINVAL</b><ul compact><li>An 67invalid flag value or parameter was specified.</ul> 68<br> 69<hr size=1 noshade> 70<b>Description: DbEnv::get_mp_max_write</b> 71<p>The DbEnv::get_mp_max_write method returns the current maximum number of 72sequential write operations and microseconds to pause.</p> 73<p>The DbEnv::get_mp_max_write method may be called at any time during the life of the 74application.</p> 75<p>The DbEnv::get_mp_max_write method 76either returns a non-zero error value 77or throws an exception that encapsulates a non-zero error value on 78failure, and returns 0 on success. 79</p> 80<b>Parameters</b> <br> 81 <b>maxwritep</b><ul compact><li>The <b>maxwritep</b> parameter references memory into which 82 the maximum number of sequential write operations is copied.</ul> 83 <b>maxwrite_sleepp</b><ul compact><li>The <b>maxwrite_sleepp</b> parameter references memory into which 84 the microseconds to pause before scheduling further write operations is copied.</ul> 85<br> 86<hr size=1 noshade> 87<br><b>Class</b> 88<a href="/api_cxx/env_class.html">DbEnv</a>, <a href="/api_cxx/mempfile_class.html">DbMpoolFile</a> 89<br><b>See Also</b> 90<a href="/api_cxx/memp_list.html">Memory Pools and Related Methods</a> 91</tt> 92<table width="100%"><tr><td><br></td><td align=right> 93<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> 94</td></tr></table> 95<p><font size=1>Copyright (c) 1996,2008 Oracle. All rights reserved.</font> 96</body> 97</html> 98
