xXx

Hexid M1n1 5h3ll MobiLe

proc/2213/root/usr/local/java/db/docs/html/devguide/_[ Not.Writable ]

File://proc/2213/root/usr/local/java/db/docs/html/devguide/cdevconcepts36402.html

<!--
  Licensed to the Apache Software Foundation (ASF) under one or more
  contributor license agreements.  See the NOTICE file distributed with
  this work for additional information regarding copyright ownership.
  The ASF licenses this file to You under the Apache License, Version 2.0
  (the "License"); you may not use this file except in compliance with
  the License.  You may obtain a copy of the License at

      http://www.apache.org/licenses/LICENSE-2.0

  Unless required by applicable law or agreed to in writing, software
  distributed under the License is distributed on an "AS IS" BASIS,
  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  See the License for the specific language governing permissions and
  limitations under the License.
-->
<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html lang="en-us" xml:lang="en-us">
<head>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type" />
<meta name="copyright" content="(C) Copyright 2005" />
<meta name="DC.rights.owner" content="(C) Copyright 2005" />
<meta content="public" name="security" />
<meta content="index,follow" name="Robots" />
<meta http-equiv="PICS-Label" content='(PICS-1.1 "http://www.icra.org/ratingsv02.html" l gen true r (cz 1 lz 1 nz 1 oz 1 vz 1) "http://www.rsac.org/ratingsv01.html" l gen true r (n 0 s 0 v 0 l 0) "http://www.classify.org/safesurf/" l gen true r (SS~~000 1))' />
<meta content="concept" name="DC.Type" />
<meta name="DC.Title" content="Types and scope of locks in Derby systems" />
<meta name="abstract" content="There are several types of locks available in Derby systems, including exclusive, shared, and update locks." />
<meta name="description" content="There are several types of locks available in Derby systems, including exclusive, shared, and update locks." />
<meta content="Locks, exclusive, shared, update" name="DC.subject" />
<meta content="Locks, exclusive, shared, update" name="keywords" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts15366.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts22300.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts23810.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts28436.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts30291.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts842279.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts842304.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts842385.html" />
<meta scheme="URI" name="DC.Relation" content="rdevconcepts2462.html" />
<meta scheme="URI" name="DC.Relation" content="rdevconcepts8424.html" />
<meta scheme="URI" name="DC.Relation" content="cdevconcepts842613.html" />
<meta content="XHTML" name="DC.Format" />
<meta content="cdevconcepts36402" name="DC.Identifier" />
<meta content="en-us" name="DC.Language" />
<link href="commonltr.css" type="text/css" rel="stylesheet" />
<title>Types and scope of locks in Derby systems</title>
</head>
<body id="cdevconcepts36402"><a name="cdevconcepts36402"><!-- --></a>


<h1 class="topictitle1">Types and scope of locks in Derby systems</h1>



<div><p>There are several types of locks available in <span>Derby</span> systems,
including exclusive, shared, and update locks.</p>
</div>

<div>
<ul class="ullinks">
<li class="ulchildlink"><strong><a href="cdevconcepts842279.html">Exclusive locks</a></strong><br />
When a statement modifies data, its transaction holds an exclusive lock on data that prevents other transactions from accessing the data.</li>
<li class="ulchildlink"><strong><a href="cdevconcepts842304.html">Shared locks</a></strong><br />
When a statement reads data without making any modifications, its transaction obtains a shared lock on the data.</li>
<li class="ulchildlink"><strong><a href="cdevconcepts842385.html">Update locks</a></strong><br />
When a user-defined update cursor (created with the FOR UPDATE clause or by using concurrency mode ResultSet.CONCUR_UPDATABLE) reads data, its transaction obtains an update lock on the data.</li>
<li class="ulchildlink"><strong><a href="rdevconcepts2462.html">Lock compatibility</a></strong><br />
This table lists compatibility between lock types. + means the lock types are compatible, while - means they are incompatible.</li>
<li class="ulchildlink"><strong><a href="rdevconcepts8424.html">Scope of locks</a></strong><br />
The amount of data locked by a statement can vary.</li>
<li class="ulchildlink"><strong><a href="cdevconcepts842613.html">Notes on locking</a></strong><br />
In addition to the locks already described, foreign key lookups require briefly held shared locks on the referenced table (row or table, depending on the configuration).</li>
</ul>

<div class="familylinks">
<div class="parentlink"><strong>Parent topic:</strong> <a href="cdevconcepts30291.html" title="This section discusses topics pertinent to multi-user systems, in which concurrency is important.">Locking, concurrency, and isolation</a></div>
</div>
<div class="relconcepts"><strong>Related concepts</strong><br />
<div><a href="cdevconcepts15366.html" title="Derby provides four transaction isolation levels. Setting the transaction isolation level for a connection allows a user to specify how severely the user's transaction should be isolated from other transactions.">Isolation levels and concurrency</a></div>
<div><a href="cdevconcepts22300.html" title="If a connection does not specify its isolation level, it inherits the default isolation level for the Derby system. The default value is CS.">Configuring isolation levels</a></div>
<div><a href="cdevconcepts23810.html" title="Derby can be configured for table-level locking. With table-level locking, when a transaction locks data in order to prevent any transaction anomalies, it always locks the entire table, not just those rows being accessed.">Lock granularity</a></div>
<div><a href="cdevconcepts28436.html" title="In a database, a deadlock is a situation in which two or more transactions are waiting for one another to give up locks.">Deadlocks</a></div>
</div>
</div>

</body>
</html>

Your Access Expired	Date. in : 17-08-2025
Regist : 09-12-2024	Expired : 01-12-2027