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diff --git a/db/docs/ref/debug/common.html b/db/docs/ref/debug/common.html new file mode 100644 index 000000000..6374307f1 --- /dev/null +++ b/db/docs/ref/debug/common.html @@ -0,0 +1,109 @@ +<!--$Id: common.so,v 10.13 2000/12/05 18:04:26 bostic Exp $--> +<!--Copyright 1997, 1998, 1999, 2000 by Sleepycat Software, Inc.--> +<!--All rights reserved.--> +<html> +<head> +<title>Berkeley DB Reference Guide: Common errors</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>Debugging Applications</dl></h3></td> +<td width="1%"><a href="../../ref/debug/printlog.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/build_unix/intro.html"><img src="../../images/next.gif" alt="Next"></a> +</td></tr></table> +<p> +<h1 align=center>Common errors</h1> +<p>This page outlines some of the most common problems that people encounter +and some suggested courses of action. +<p><dl compact> +<p><dt><b>Symptom:</b><dd>Core dumps or garbage returns from random Berkeley DB operations. +<p><dt>Possible Cause:<dd>Failure to zero out DBT structure before issuing request. +<p><dt>Fix:<dd>Before using a <a href="../../api_c/dbt.html">DBT</a>, you must initialize all its elements +to 0 and then set the ones you are using explicitly. +<p><dt><b>Symptom:</b><dd>Random crashes and/or database corruption. +<p><dt>Possible Cause:<dd>Running multiple threads, but did not specify <a href="../../api_c/env_open.html#DB_THREAD">DB_THREAD</a> +to <a href="../../api_c/db_open.html">DB->open</a> or <a href="../../api_c/env_open.html">DBENV->open</a>. +<p><dt>Fix:<dd>Any time you are sharing a handle across multiple threads, you must +specify <a href="../../api_c/env_open.html#DB_THREAD">DB_THREAD</a> when you open that handle. +<p><dt><b>Symptom:</b><dd><a href="../../api_c/env_open.html">DBENV->open</a> returns EINVAL. +<p><dt>Possible Cause:<dd>The environment home directory is a remote mounted filesystem. +<p><dt>Fix:<dd>Use a locally mounted filesystem instead. +<p><dt><b>Symptom:</b><dd><a href="../../api_c/db_get.html">DB->get</a> calls are returning EINVAL. +<p><dt>Possible Cause:<dd>The application is running with threads, but did not specify the +<a href="../../api_c/dbt.html#DB_DBT_MALLOC">DB_DBT_MALLOC</a>, <a href="../../api_c/dbt.html#DB_DBT_REALLOC">DB_DBT_REALLOC</a> or <a href="../../api_c/dbt.html#DB_DBT_USERMEM">DB_DBT_USERMEM</a> +flags in the <a href="../../api_c/dbt.html">DBT</a> structures used in the call. +<p><dt>Fix:<dd>When running with threaded handles (i.e., specifying <a href="../../api_c/env_open.html#DB_THREAD">DB_THREAD</a> +to <a href="../../api_c/env_open.html">DBENV->open</a> or <a href="../../api_c/db_open.html">DB->open</a>), you must specify one of those +flags for all <a href="../../api_c/dbt.html">DBT</a> structures in which Berkeley DB is returning data. +<p><dt><b>Symptom:</b><dd>Running multiple threads or processes, and the database appears to be +getting corrupted. +<p><dt>Possible Cause:<dd>Locking is not enabled. +<p><dt>Fix:<dd>Make sure that you are acquiring locks in your access methods. You +must specify <a href="../../api_c/env_open.html#DB_INIT_LOCK">DB_INIT_LOCK</a> to your <a href="../../api_c/env_open.html">DBENV->open</a> call and then +pass that environment to <a href="../../api_c/db_open.html">DB->open</a>. +<p><dt><b>Symptom:</b><dd>Locks are accumulating or threads and/or processes are +deadlocking even though there is no concurrent access to the database. +<p><dt>Possible Cause:<dd>Failure to close a cursor. +<p><dt>Fix:<dd>Cursors retain locks between calls. Everywhere the application uses +a cursor, the cursor should be explicitly closed as soon as possible after +it is used. +<p><dt><b>Symptom:</b><dd>The system locks up. +<p><dt>Possible Cause:<dd>Application not checking for <a href="../../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a>. +<p><dt>Fix:<dd>Unless you are using the Concurrent Data Store product, whenever you +have multiple threads and/or processes and at least one of them is +writing, you have the potential for deadlock. As a result, you must +test for the <a href="../../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> return on every Berkeley DB call. In +general, updates should take place in a transaction or you might leave +the database in an inconsistent state. Reads may take place outside +the context of a transaction under common conditions. +<p>Whenever you get a <a href="../../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> return, you should: +<p><ol> +<p><li>If you are running in a transaction, abort the transaction, first closing +any cursors opened in the transaction. +<p><li>If you are not running in a transaction, simply close the cursor that got +the <a href="../../ref/program/errorret.html#DB_LOCK_DEADLOCK">DB_LOCK_DEADLOCK</a> (if it was a cursor operation) and retry. +</ol> +<p>See <a href="../../ref/transapp/put.html">Recoverability and deadlock +avoidance</a> for further information. +<p><dt><b>Symptom:</b><dd>An inordinately high number of deadlocks. +<p><dt>Possible Cause:<dd>Read-Modify-Write pattern without using the RMW flag. +<p><dt>Fix:<dd>If you frequently read a piece of data, modify it and then write +it, you may be inadvertently causing a large number of deadlocks. Try +specifying the <a href="../../api_c/dbc_get.html#DB_RMW">DB_RMW</a> flag on your get calls. +<p>Or, if the application is doing a large number of updates in a small +database, turning off Btree splits may help (see <a href="../../api_c/db_set_flags.html#DB_REVSPLITOFF">DB_REVSPLITOFF</a> +for more information.) +<p><dt><b>Symptom:</b><dd>I run recovery and it exits cleanly, but my database changes are missing. +<p><dt>Possible Cause:<dd>Failure to enable logging and transactions in the database environment, +failure to specify DB_ENV handle when creating DB handle, +transaction handle not passed to Berkeley DB interface, failure to commit +transaction. +<p><dt>Fix:<dd>Make sure that the environment and database handles are properly +created, and that the application passes the transaction handle returned +by <a href="../../api_c/txn_begin.html">txn_begin</a> to the appropriate Berkeley DB interfaces, and that each +transaction is eventually committed. +<p><dt><b>Symptom:</b><dd>Recovery fails. +<p><dt>Possible Cause:<dd>A database was updated in a transactional environment both with and +without transactional handles. +<p><dt>Fix:<dd>If any database write operation is done using a transaction handle, +every write operation must be done in the context of a transaction. +<p><dt><b>Symptom:</b><dd>A database environment locks up, sometimes gradually. +<p><dt>Possible Cause:<dd>A thread of control exited unexpectedly, holding Berkeley DB resources. +<p><dt>Fix:<dd>Whenever a thread of control exits holding Berkeley DB resources, all threads +of control must exit the database environment, and recovery must be run. +<p><dt><b>Symptom:</b><dd>A database environment locks up, sometimes gradually. +<p><dt>Possible Cause:<dd>Cursors are not being closed before transaction abort. +<p><dt>Fix:<dd>Before an application aborts a transaction, any cursors opened within +the context of that transaction must be closed. +<p><dt><b>Symptom:</b><dd>Transaction abort or recovery fail, or database corruption occurs. +<p><dt>Possible Cause:<dd>Log files were removed before it was safe. +<p><dt>Fix:<dd>Do not remove any log files from a database environment until Berkeley DB +declares it safe. +</dl> +<table><tr><td><br></td><td width="1%"><a href="../../ref/debug/printlog.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/build_unix/intro.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> |