ORA-01031 insufficient privileges

Developer was getting "ORA-01031: insufficient privileges" error while updating a table even though the user had proper privileges already. Complete scenario is given below 


Scenario:
1- Developer created a role "myrole"
create role myrole;
2- Assign some DML grants to this role "myrole"
GRANT DELETE, INSERT, SELECT, UPDATE ON T1 TO myrole -- role
3- Assign role "myrole" to a user "USER1"
grant myrole to USER1;
4- Connected to the user "USER1" and ran update statment
update T1 set c1 ='a' where user_id='ABC'
5- got the below error , why as the privileges already given to user through role.
ORA-01031: insufficient privileges

Cause:
The error occurred because the role was not active in the user session as it was not a default role.

you can check the active sessions by query below
SQL> select * from session_roles;

You can perform these steps to resolve the issue:

sqlplus / as sysdba
alter user USER1 default role all;

connect user1
select * from session_roles;update T1 set c1 ='a' where user_id='ABC'

Note:
You may create the scripts for all users if required.
select 'ALTER USER '||username||' DEFAULT ROLE ALL;'
from dba_users
where username like 'APP_%'