By default Tomcat (the bundled web server) is configured to use a maximum of 768 MB 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 2 GB i.e. 2048 MB.
Set the system environment
variable CATALINA_OPTS to -Xmx2048M (Note the
dash in front of the X)
On Microsoft Windows
Right click on My Computer
Click Properties
Click on the Advanced tab (or click on Advanced system settings in Windows Vista)
Click the button
Under System variables, click
Set variable name to CATALINA_OPTS and variable
value to -Xmx2048M
Click
Click 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=-Xmx2048M
Save the file
Logout and Login again