Instalación y actualización > Upgrade Guide > The Windchill Upgrade Procedure > Setting Up the Target System for Upgrade > Increase the Method Server Heap Size (Optional)
  
Increase the Method Server Heap Size (Optional)
For some sites, migrators, WinDU tasks and other tools may fail with Out of Memory Exceptions because of the lower heap size default setting. To prevent these errors, perform the following.
Using xconfmanager, update the site.xconf file by adding or changing the following properties based on available memory on your installation:
wt.method.maxHeap
wt.method.minHeap
com.ptc.windchill.upgrade.tools.java.args