How to update mass permission

Recently in my company my manager allocated me work to update permission set for 500 users in salesforce org.

How i updated what i did , should i update manually?

I saw there was specific permission which should be update to all user

I simply collect the permission set id of that permission set from permissionset object.

I made a excel containing user name and having that permission set id

I did data import on permission assignment object .

What was error or problem i face during this?

I face error related custom tab limit where it was saying to expand custom tab size

Solution: I just reduce my batch size from 200 to 1 .

I did successful update of permission .