1<!--$Id: env_set_thread_count.so,v 10.3 2007/04/02 16:08:13 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_thread_count</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_thread_count</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_thread_count(u_int32_t count); 26<p> 27int 28DbEnv::get_thread_count(u_int32_t *countp); 29</pre></b> 30<hr size=1 noshade> 31<b>Description: DbEnv::set_thread_count</b> 32<p>Declare an approximate number of threads in the database environment. 33The DbEnv::set_thread_count method must be called prior to opening the 34database environment if the <a href="../api_cxx/env_failchk.html">DbEnv::failchk</a> method will be used. The 35DbEnv::set_thread_count method does not set the maximum number of 36threads but is used to determine memory sizing and the thread control 37block reclamation policy.</p> 38<p>If a process has not configured an <b>is_alive</b> function from the 39<a href="../api_cxx/env_set_isalive.html">DbEnv::set_isalive</a> method, and then attempts to join a database 40environment configured for failure checking with the 41<a href="../api_cxx/env_failchk.html">DbEnv::failchk</a>, <a href="../api_cxx/env_set_thread_id.html">DbEnv::set_thread_id</a>, 42<a href="../api_cxx/env_set_isalive.html">DbEnv::set_isalive</a> and DbEnv::set_thread_count methods, the 43program may be unable to allocate a thread control block and fail to 44join the environment. 45<b>This is true of the standalone Berkeley DB utility programs.</b> 46To avoid problems when using the standalone Berkeley DB utility programs with 47environments configured for failure checking, incorporate the utility's 48functionality directly in the application, or call the 49<a href="../api_cxx/env_failchk.html">DbEnv::failchk</a> method before running the utility.</p> 50<p>The database environment's thread count may also be configured using the 51environment's <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file. The syntax of the entry in that 52file is a single line with the string "set_thread_count", one or more whitespace 53characters, and the thread count. 54Because the <a href="../ref/env/db_config.html#DB_CONFIG">DB_CONFIG</a> file is read when the database environment 55is opened, it will silently overrule configuration done before that 56time.</p> 57<p>The DbEnv::set_thread_count method configures operations performed using the specified 58<a href="../api_cxx/env_class.html">DbEnv</a> handle, not all operations performed on the underlying 59database environment.</p> 60<p>The DbEnv::set_thread_count method may not be called after the <a href="../api_cxx/env_open.html">DbEnv::open</a> method is 61called. 62</p> 63<p>The DbEnv::set_thread_count method 64either returns a non-zero error value 65or throws an exception that encapsulates a non-zero error value on 66failure, and returns 0 on success. 67</p> 68<b>Parameters</b> <br> 69 <b>count</b><ul compact><li>The <b>count</b> parameter is an approximate thread count for the 70database environment.</ul> 71<br> 72<br><b>Errors</b> 73<p>The DbEnv::set_thread_count method 74may fail and throw 75<a href="../api_cxx/except_class.html">DbException</a>, 76encapsulating one of the following non-zero errors, or return one of 77the following non-zero errors:</p> 78<br> 79<b>EINVAL</b><ul compact><li>If the method was called after <a href="../api_cxx/env_open.html">DbEnv::open</a> was called; or if an 80invalid flag value or parameter was specified.</ul> 81<br> 82<hr size=1 noshade> 83<b>Description: DbEnv::get_thread_count</b> 84<p>The DbEnv::get_thread_count method returns the thread count.</p> 85<p>The DbEnv::get_thread_count method may be called at any time during the life of the 86application.</p> 87<p>The DbEnv::get_thread_count method 88either returns a non-zero error value 89or throws an exception that encapsulates a non-zero error value on 90failure, and returns 0 on success. 91</p> 92<b>Parameters</b> <br> 93 <b>countp</b><ul compact><li>The DbEnv::get_thread_count method returns the 94thread count in <b>countp</b>.</ul> 95<br> 96<hr size=1 noshade> 97<br><b>Class</b> 98<a href="../api_cxx/env_class.html">DbEnv</a> 99<br><b>See Also</b> 100<a href="../api_cxx/env_list.html">Database Environments and Related Methods</a> 101</tt> 102<table width="100%"><tr><td><br></td><td align=right> 103<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> 104</td></tr></table> 105<p><font size=1>Copyright (c) 1996,2008 Oracle. 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