Partnership Dissolution

GANTA NARENDRA BABU (Self Employed) (41 Points)

27 October 2017  
A registered partnership firm having a two parners and carried business from past two years, now the existing two partners want to retire and join two new partners.
Now my question is it is called as reconstruction of the firm or Dissolution of the firm.
Second question is if all the partners retired and join a new partners at same time can be done or not.