If you are experiencing problems with Tomcat crashing because of OutOfMemory errors and you have tried increasing the available heap size without success then log into the Tomcat manager (normally http://localhost:8080/manager/html/list) and click on the Server Status link at the top of the page.
At the bottom of the Server Status page is a list of currently running requests. Monitoring this page for requests that are taking a long time to complete (or not completing at all) is a good way of identifying actions that could be spiralling out of control.
One example action that experienced this problem in older versions of Asset Bank is the 'add all search results to asset box' action. Up until recently this action had the potential to use large amounts of memory if it was requested for a very large number of search or browse results. In more recent versions a limit has been placed on the number of assets that can be added to the asset box from this action.