Unable to drop users as SYS

Hi all,

I'm trying to drop several users from the DB using SYS account.

However when I issue the command drop user xx cascade, I'm receiving ORA-04063 errors. Please see example below.

SQL> drop user ADMIN_UTILS cascade;

drop user ADMIN_UTILS

*

ERROR at line 1:

ORA-04063: CLIENT_QTAB has errors

Weirdly it only happen on those few users, I didn't face any issue when I tried to drop a dummy account i created on the db.

SQL> create user testing identified by test;

User created.

SQL> drop user testing cascade;

User dropped.

I did check on the table which is having the error & found the table is invalid. Can anyone help me to resolve this? I'm at lost right now because I'm not able to find much info regarding validating invalid table from google or MOS.