Issue with retrieveProperties

Hi,

I am using VMWare SDK Web Service API to monitor and collect the performance statistics. I am trying to retrieve performance statistics (Historical Intervals) from vCenter. Here is the piece of code for this.

private ObjectContent[] getManagerContents(PropertySpec propertySpec, ManagedObjectReference ref) throws Exception

    {

        PropertySpec[] propspecary = new PropertySpec[]{ propertySpec };

        PropertyFilterSpec spec = new PropertyFilterSpec();

        spec.setPropSet(propspecary);

        spec.setObjectSet(new ObjectSpec[]{new ObjectSpec()});

        spec.getObjectSet(0).setObj(ref);

        spec.getObjectSet(0).setSkip(new Boolean(false));

        return cb.getConnection().getService().retrieveProperties(cb.getConnection().getServiceContent().getPropertyCollector(), new PropertyFilterSpec[]{spec});

   }

The above method works most of the time, but some times returns blank ObjectContent. I would like to know in which case it will return blank array of ObjectContent.

Any help would be greatly appreciated.

Thanks,