Often time, Tomcat may hits the following java.lang.OutOfMemoryError: PermGen space error.

java.lang.OutOfMemoryError: PermGen space
at java.lang.ClassLoader.defineClass1(Native Method)
at java.lang.ClassLoader.defineClass(ClassLoader.java:620)
at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:124)
It’s usually happened after the Tomcat restarts a few times.

1. Solution
By default, Tomcat is assigned a very little PermGen memory for the running process. To fix it, increase the PermGen memory settings by using the following Java VM options.

-XX:PermSize<size> - Set initial PermGen Size.
-XX:MaxPermSize<size> - Set the maximum PermGen Size.
In the next step, we will show you how to set the VM options in Tomcat, under Windows and Linux environment.

2. Windows
Tomcat is managed by this script file catalina.bat, dive inside the script, you will find out that catalina.bat always find and run the setenv.bat file to set the environment variables.

{$tomcat-folder}\bin\catalina.bat
//...
rem Get standard environment variables
if not exist "%CATALINA_BASE%\bin\setenv.bat" goto checkSetenvHome
call "%CATALINA_BASE%\bin\setenv.bat"
goto setenvDone
:checkSetenvHome
if exist "%CATALINA_HOME%\bin\setenv.bat" call "%CATALINA_HOME%\bin\setenv.bat"
:setenvDone
//...
2.1 To set the environment variable on Windows, create a setenv.bat manually, and put it into the ${tomcat-folder}\bin folder.

${tomcat-folder}\bin\setenv.bat
set JAVA_OPTS=-Dfile.encoding=UTF-8 -Xms128m -Xmx1024m -XX:PermSize=64m -XX:MaxPermSize=256m
P.S No double quotes, set JAVA_OPTS={value}.

2.2 Restart Tomcat, it will call the setenv.bat file to set the environment variable automatically.

{$tomcat-folder}\bin\catalina.bat restart

Tomcat java.lang.OutOfMemoryError: PermGen space error