做项目的时候，突然遇到的这个问题，当时tomcat开启了有2个小时，然后点击页面的时候出现：PermGen space
在网上查找了好久，终于找到了解决办法。
转载：http://www.cnblogs.com/xwdreamer/archive/2011/11/21/2296930.html
在看下文之前，首先要确认意见事情，就是你是如何启动tomcat的，我们在平时的开发环境当中，都是通过startup.bat方式启动tomcat的，那么你按照下面的方式，去修改/bin/catalina.bat是没有问题的。但是如果你是生产环境下，我们一般都希望使用windows服务方式去启动tomcat，此时之前修改的配置文件是没有用的。因为windows服务启动tomcat不再去加载catalina.bat当中的参数了，而是去加载注册表中的参数，所以我们需要修改注册表。
HKEY_LOCAL_MACHINE/SOFTWARE/Apache Software Foundation/Procrun 2.0/Tomcat_APPNAME/Parameters/Java，修改JvmMs和JvmMx的值，当前我都将其设定为1024，也就是1个G的容量。具体性能再后面继续观察。 之前还真不知道windows服务启动和startup.bat启动的区别。 windows服务器启动是在注册表中加载参数，startup.bat启动是在catalina.bat加载参数。
1.参考：
2.报错：
Exception in thread "DispatcherThread" java.lang.OutOfMemoryError: PermGen spaceException in thread "ContainerBackgroundProcessor[StandardEngine[Catalina]]" java.lang.OutOfMemoryError: PermGen spaceException in thread "State Saver" java.lang.OutOfMemoryError: PermGen spaceException in thread "AWT-Windows" java.lang.OutOfMemoryError: OutOfMemoryError
3.原因：
PermGen space的全称是Permanent Generation space,是指内存的永久保存区域,这块内存主要是被JVM存放Class和Meta信息的,Class在被Loader时就会被放到PermGen space中,它和存放类实例(Instance)的Heap区域不同,GC(Garbage Collection)不会在主程序运行期对PermGen space进行清理，所以如果你的应用中有很多CLASS的话,就很可能出现PermGen space错误,这种错误常见在web服务器对JSP进行pre compile的时候。如果你的WEB APP下都用了大量的第三方jar, 其大小超过了jvm默认的大小(4M)那么就会产生此错误信息了。
4.解决方法1：
手动设置MaxPermSize大小，如果是linux系统，修改TOMCAT_HOME/bin/catalina.sh，如果是windows系统，修改TOMCAT_HOME/bin/catalina.bat，
在“echo "Using CATALINA_BASE: $CATALINA_BASE"”上面加入以下行：JAVA_OPTS="-server -XX:PermSize=64M -XX:MaxPermSize=128m建议：将相同的第三方jar文件移置到tomcat/shared/lib目录下，这样可以达到减少jar 文档重复占用内存的目的。5.解决方法2
修改eclipse.ini文件，修改如下：
-vmargs-Dosgi.requiredJavaVersion=1.5-Xms128m-Xmx512m-XX:PermSize=64M -XX:MaxPermSize=128M
如果还报错，可以考虑如下修改
-vmargs-Dosgi.requiredJavaVersion=1.5-Xms512m-Xmx1024m-XX:PermSize=256M -XX:MaxPermSize=512M
报错：
2011-11-21 21:10:46 org.apache.catalina.loader.WebappClassLoader clearReferencesJdbc严重: The web application [/Application] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.2011-11-21 21:10:46 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads严重: The web application [/Application] appears to have started a thread named [MySQL Statement Cancellation Timer] but has failed to stop it. This is very likely to create a memory leak.2011-11-21 21:10:46 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads严重: The web application [/Application] appears to have started a thread named [AWT-Windows] but has failed to stop it. This is very likely to create a memory leak.2011-11-21 21:10:46 org.apache.catalina.loader.WebappClassLoader clearReferencesThreads严重: The web application [/Application] appears to have started a thread named [Thread-14] but has failed to stop it. This is very likely to create a memory leak.2011-11-21 21:10:46 org.apache.catalina.loader.WebappClassLoader clearThreadLocalMap严重: The web application [/Application] created a ThreadLocal with key of type [net.sf.json.AbstractJSON$1] (value [net.sf.json.AbstractJSON$1@3661eeb]) and a value of type [java.util.HashSet] (value [[]]) but failed to remove it when the web application was stopped. This is very likely to create a memory leak.2011-11-21 21:10:50 org.apache.catalina.core.ApplicationContext log信息: Initializing Spring FrameworkServlet 'Dispatcher'
修改catalina.bat
添加
JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms1536m -Xmx1536m-XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+DisableExplicitGC"
样例
# JSSE_HOME (Optional) May point at your Java Secure Sockets Extension# (JSSE) installation, whose JAR files will be added to the# system class path used to start Tomcat.## CATALINA_PID (Optional) Path of the file which should contains the pid# of catalina startup java process, when start (fork) is used## $Id: catalina.sh 609438 2008-01-06 22:14:28Z markt $# ----------------------------------------------------------------------------- JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms1536m -Xmx1536m -XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+DisableExplicitGC" # OS specific support. $var _must_ be set to either true or false.cygwin=falseos400=falsedarwin=falsecase "`uname`" inCYGWIN*) cygwin=true;;OS400*) os400=true;;Darwin*) darwin=true;;esac # resolve links - $0 may be a softlinkPRG="$0"
具体参数根据自己机器情况而定
JAVA_OPTS="-Djava.awt.headless=true -Dfile.encoding=UTF-8 -server -Xms512m -Xmx512m -XX:NewSize=256m -XX:MaxNewSize=256m -XX:PermSize=256m -XX:MaxPermSize=256m -XX:+DisableExplicitGC"