Trouble with P6 r8 integration API

Hello all,

I want to update Physical percent complete of an activity using the integration api. To do that I am setting 

  Task status to "IN_PROGRESS"

  Percent Complete Type to "PHYSICAL"

  Physical Percent Complete to 20%

Code snippet 

     a.setPercentCompleteType(PercentCompleteType.PHYSICAL);

      a.setStatus(ActivityStatus.IN_PROGRESS);

      a.setPhysicalPercentComplete(new Percent(0.20);

However the code does not update the activity physical percent complete. Has any one used Integration API to update Physical percent complete for an activity?

Any help will be appreciated.

Thanks,

Sachin