By default Tomcat (the bundled web server) is configured to use a maximum of 2 GB of memory which is quite sufficient in majority of cases. In case this proves insufficient for you, you can increase it as follows:

First determine the amount of memory you want to allocate. Typically, it should not exceed half of your installed RAM. For example, if you have 4 GB of RAM, then you can safely allocate 2 GB to Tomcat. Let's assume you want to set it to 4 GB i.e. 4000 MB.
Stop Celoxis
Set the system environment variable CATALINA_OPTS to -Xms512M -Xmx4000M (Note the dash in front of the X.)

On Microsoft Windows:

Right click My Computer.
Click Properties.
Click the Advanced tab (or click Advanced system settings in Windows Vista).
Click the Environment Variables button
Under System variables, click New.
Set variable name to CATALINA_OPTS and variable value to -Xms512M -Xmx4000M
Click OK.
Click OK on the Advanced tab to close the window.

On Linux:

Open a terminal and login as the user that starts Celoxis.
In the appropriate profile file (e.g. .bash_profile or .profile), type: export CATALINA_OPTS=-Xms512M -Xmx4000M
Save the file.
Logout and Login again.
Start Celoxis.

Celoxis needs to start with a minimum of 512 MB and hence, we set the -Xms value to 512M.

For 32-bit operating system, you need to set both the -Xms and -Xmx parameters as seen in the above screenshot. However, the Xmx parameter should only be set to 1GB i.e 1024M.

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