A quick one: I began to have this problem on 12c’s backup catalog schemas. The reason is that by now all information is protected by policies (VPD). The error:
EXP-00079: Data in table "&TABLE" is protected. Conventional path may only be exporting partial table.
The solution:
catalogdb> GRANT exempt access policy TO &exp_user; Grant succeeded.
Hugs!
Matheus.