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diff --git a/bdb/docs/ref/lock/max.html b/bdb/docs/ref/lock/max.html deleted file mode 100644 index 23622909035..00000000000 --- a/bdb/docs/ref/lock/max.html +++ /dev/null @@ -1,88 +0,0 @@ -<!--$Id: max.so,v 10.2 2000/12/21 19:11:28 bostic Exp $--> -<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> -<!--All rights reserved.--> -<html> -<head> -<title>Berkeley DB Reference Guide: Configuring locking: sizing the system</title> -<meta name="description" content="Berkeley DB: An embedded database programmatic toolkit."> -<meta name="keywords" content="embedded,database,programmatic,toolkit,b+tree,btree,hash,hashing,transaction,transactions,locking,logging,access method,access methods,java,C,C++"> -</head> -<body bgcolor=white> - <a name="2"><!--meow--></a> -<table><tr valign=top> -<td><h3><dl><dt>Berkeley DB Reference Guide:<dd>Locking Subsystem</dl></h3></td> -<td width="1%"><a href="../../ref/lock/config.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/lock/nondb.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p> -<h1 align=center>Configuring locking: sizing the system</h1> -<p>The lock system is sized using the following three functions: -<p><blockquote><pre><a href="../../api_c/env_set_lk_max_locks.html">DBENV->set_lk_max_locks</a> -<a href="../../api_c/env_set_lk_max_lockers.html">DBENV->set_lk_max_lockers</a> -<a href="../../api_c/env_set_lk_max_objects.html">DBENV->set_lk_max_objects</a></pre></blockquote> -<p>The <a href="../../api_c/env_set_lk_max_locks.html">DBENV->set_lk_max_locks</a>, <a href="../../api_c/env_set_lk_max_lockers.html">DBENV->set_lk_max_lockers</a> -and <a href="../../api_c/env_set_lk_max_objects.html">DBENV->set_lk_max_objects</a> functions specify, respectively, the -maximum number of locks, lockers and locked objects supported by the -lock subsystem. The maximum number of locks is the number of locks that -can be simultaneously requested in the system. The maximum number of -lockers is the number of lockers that can simultaneously request locks -in the system. The maximum number of lock objects is the number of -objects that can simultaneously be locked in the system. Selecting -appropriate values requires an understanding of your application and -its databases. If the values are too small, then requests for locks in -an application will fail. If the values are too large, then the locking -subsystem will consume more resources than is necessary. It is better -to err in the direction of allocating too many locks, lockers and -objects as increasing the number of locks does not require large amounts -of additional resources. -<p>The recommended algorithm for selecting the maximum number of locks, -lockers and lock objects, is to run the application under stressful -conditions and then review the lock system's statistics to determine -the maximum number of locks, lockers and lock objects that were used. -Then, double these values for safety. However, in some large -applications, finer granularity of control is necessary in order to -minimize the size of the lock subsystem. -<p>The maximum number of lockers can be estimated as follows: -<ul type=disc> -<li>If the -database environment is configured to use transactions, then the maximum -number of lockers needed is the number of simultaneously active -transactions and child transactions (where a child transaction is active -until its parent commits or aborts, not until it commits or aborts). -<li>If the database environment is not configured to use transactions, then -the maximum number of lockers needed is the number of simultaneous -non-cursor operations plus an additional locker for every simultaneously -open cursor. -</ul> -<p>The maximum number of lock objects needed can be estimated as follows: -<ul type=disc> -<li>For Btree and Recno access methods, you will need, at a minimum, one -lock object per level of the database tree. (Unless keys are quite -large with respect to the page size, neither Recno nor Btree database -trees should ever be deeper than five levels.) Then, you will need one -lock object for each leaf page of the database tree that will be -simultaneously accessed. -<li>For the Queue access method you will need one lock object per record -that is simultaneously accessed. To this, add one lock object per page -that will be simultaneously accessed. (Since the Queue access method -uses fixed-length records, and the database page size is known, it is -possible to calculate the number of pages and therefore, lock objects, -required.) Deleted records skipped by a <a href="../../api_c/dbc_get.html#DB_NEXT">DB_NEXT</a> or -<a href="../../api_c/dbc_get.html#DB_PREV">DB_PREV</a> operation do not require a separate lock object. -Further, if your application is using transactions, then no database -operation will ever use more than three lock objects at any time. -<li>For the Hash access method you only need a single lock object. -</ul> -<p>For all access methods, you should then add an additional lock object -per database, for the database's metadata page. -<p>The maximum number of locks required by an application cannot be easily -estimated. It is possible to calculate a maximum number of locks by -multiplying the maximum number of lockers, times the maximum number of -lock objects, times two (two for the two possible lock modes for each -object, read and write). However, this is a pessimal value, and real -applications are unlikely to actually need that many locks. Review of -the lock subsystem statistics is the best way to determine this value. -<table><tr><td><br></td><td width="1%"><a href="../../ref/lock/config.html"><img src="../../images/prev.gif" alt="Prev"></a><a href="../../ref/toc.html"><img src="../../images/ref.gif" alt="Ref"></a><a href="../../ref/lock/nondb.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p><font size=1><a href="http://www.sleepycat.com">Copyright Sleepycat Software</a></font> -</body> -</html> |