Error during upgrade: Initial heap size set to a larger value than the maximum heap size
[exec] [exec] Error occurred during initialization of VM
[exec] [exec] Initial heap size set to a larger value than the maximum heap size
This Java error indicates that the initial JVM heap (-Xms) was larger than the (-Xmx)
defaultScriptMaxMem=2560m
defaultScriptPermGenMem=512m
If you're missing the 'm' at the end, the value will be in bytes and this will make it smaller maximum value than the initial heap.
After fixing the values, retry the upgrade.