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diff --git a/bdb/docs/ref/transapp/deadlock.html b/bdb/docs/ref/transapp/deadlock.html deleted file mode 100644 index 65765ec5903..00000000000 --- a/bdb/docs/ref/transapp/deadlock.html +++ /dev/null @@ -1,92 +0,0 @@ -<!--$Id: deadlock.so,v 10.15 2000/08/10 17:54:49 bostic Exp $--> -<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> -<!--All rights reserved.--> -<html> -<head> -<title>Berkeley DB Reference Guide: Deadlock detection</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>Transaction Protected Applications</dl></h3></td> -<td width="1%"><a href="../../ref/transapp/admin.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/transapp/checkpoint.html"><img src="../../images/next.gif" alt="Next"></a> -</td></tr></table> -<p> -<h1 align=center>Deadlock detection</h1> -<p>The first component of the infrastructure, deadlock detection, is not -so much a requirement specific to transaction protected applications, -but rather is necessary for almost all applications where more than a -single thread of control will be accessing the database at one time. -While Berkeley DB automatically handles database locking, it is normally -possible for deadlock to occur. It is not required by all transactional -applications, but exceptions are rare. -<p>When the deadlock occurs, two (or more) threads of control each request -additional locks which can never be granted because one of the threads -of control waiting holds the requested resource. -<p>For example, consider two processes A and B. Let's say that A obtains -an exclusive lock on item X, and B obtains an exclusive lock on item Y. -Then, A requests a lock on Y and B requests a lock on X. A will wait -until resource Y becomes available and B will wait until resource X -becomes available. Unfortunately, since both A and B are waiting, -neither will release the locks they hold and neither will ever obtain -the resource on which it is waiting. In order to detect that deadlock -has happened, a separate process or thread must review the locks -currently held in the database. If deadlock has occurred, a victim must -be selected, and that victim will then return the error -<a href="../../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> from whatever Berkeley DB call it was making. -<p>Berkeley DB provides a separate UNIX-style utility which can be used to -perform this deadlock detection, named <a href="../../utility/db_deadlock.html">db_deadlock</a>. -Alternatively, applications can create their own deadlock utility or -thread using the underlying <a href="../../api_c/lock_detect.html">lock_detect</a> function, or specify -that Berkeley DB run the deadlock detector internally whenever there is a -conflict over a lock (see <a href="../../api_c/env_set_lk_detect.html">DBENV->set_lk_detect</a> for more -information). The following code fragment does the latter: -<p><blockquote><pre>void -env_open(DB_ENV **dbenvp) -{ - DB_ENV *dbenv; - int ret; -<p> - /* Create the environment handle. */ - if ((ret = db_env_create(&dbenv, 0)) != 0) { - fprintf(stderr, - "txnapp: db_env_create: %s\n", db_strerror(ret)); - exit (1); - } -<p> - /* Set up error handling. */ - dbenv->set_errpfx(dbenv, "txnapp"); -<p> -<b> /* Do deadlock detection internally. */ - if ((ret = dbenv->set_lk_detect(dbenv, DB_LOCK_DEFAULT)) != 0) { - dbenv->err(dbenv, ret, "set_lk_detect: DB_LOCK_DEFAULT"); - exit (1); - }</b> -<p> - /* - * Open a transactional environment: - * create if it doesn't exist - * free-threaded handle - * run recovery - * read/write owner only - */ - if ((ret = dbenv->open(dbenv, ENV_DIRECTORY, - DB_CREATE | DB_INIT_LOCK | DB_INIT_LOG | - DB_INIT_MPOOL | DB_INIT_TXN | DB_RECOVER | DB_THREAD, - S_IRUSR | S_IWUSR)) != 0) { - dbenv->err(dbenv, ret, "dbenv->open: %s", ENV_DIRECTORY); - exit (1); - } -<p> - *dbenvp = dbenv; -}</pre></blockquote> -<p>Deciding how often to run the deadlock detector and which of the -deadlocked transactions will be forced to abort when the deadlock is -detected is a common tuning parameter for Berkeley DB applications. -<table><tr><td><br></td><td width="1%"><a href="../../ref/transapp/admin.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/transapp/checkpoint.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> |