The GMU (Gateway Migration Utility) uses Java. If you are using a Windows machine to run the utility, you will notice the amount of Java memory increasing while the utility is running. You can observe this via task manager.
The utility may stop at the same point in memory usage every time with the following error:
Execution failed. Reason: Java heap space.
The machine may have a lot of memory but be limited on Java Memory
Check the max amount of Java memory allocated to the machine.
java -XX:+PrintFlagsFinal -version | findstr HeapSize
Look at the MaxHeapSize value. For example :
uintx MaxHeapSize = 4280287232
If you have a significantly lower value than the above, your overall memory allocation to the machine may need to be increased and/or your Java settings modified to increase the Max Java Heap size.