The affix ghañ comes after the verb stu 'to praise' when it is preceded by the upasarga sam and the word refers to sacrificial subjects.,
As संस्तावश्छन्दोगानाम् 'the Sanstava of the Chhandogas'; संस्ताव (= समेत्य स्तुवन्ति यस्मिन् देशे छन्दोगाः स देशः) means 'the place which the Brahmanas repeating hymns and prayers, occupy at a sacrifice'.
But when not referring to sacrifice we have संस्तवश्छात्रयोः 'the praising together of the two pupils'.,