Offline data support in hybrid mobile app

I am creating a hybrid mobile app using ionic and angular as front end and node as the back end. Its an app for an already existing CRM. The requirement is to have the offline data support which means the user can occasionally sync the data from the server and can view all the data while he is offline too. The problem is that the amount of data here can be enormous. I want to know what is the proper approach to design such an architecture which can be scalable and robust. I see that there is a requirement to save the data locally on the mobile app itself. What should be the approach I should follow. Do I need to save replica of the whole database on front end itself? Thanks in advance!