Instrument not found after closing the VI reference

Hi ,

We are calling  two VI's in Teststand, out of which one VI initializes the instrument and other VI does the measurement. After the initialize VI is called i am closing the reference for the initialize VI due to which  instrument not found error is coming in measurement VI. If the reference is kept open the error is not coming, i want to ask does closing the VI reference has any effect on VISA resource also?

Thanks