code: public Object execute(final Map<Object, Object> iArgs) {
      if (attribute == null)
        throw new OCommandExecutionException("Cannot execute the command because it has not yet been parsed");
  
      final OClassImpl sourceClass = (OClassImpl) getDatabase().getMetadata().getSchema().getClass(className);
      if (sourceClass == null)
        throw new OCommandExecutionException("Source class '" + className + "' not found");
  
      final OPropertyImpl prop = (OPropertyImpl) sourceClass.getProperty(fieldName);
      if (prop == null)
        throw new OCommandExecutionException("Property '" + className + "." + fieldName + "' not exists");
  
      prop.setInternalAndSave(attribute, value);
      return null;
    }
docs: Execute the ALTER PROPERTY.