STS Drop Caused error

select name,STATEMENT_COUNT from dba_sqlset where owner = 'VAZEP';

exec dbms_sqltune.drop_sqlset('STS_BSZVN56GN9RWJ');

If you get below error while dropping STS
"ORA-13757: “SQL Tuning Set” “sts_test_01″ owned by user “badger” is active."

Then Check

select description,sqlset_name
from DBA_SQLSET_REFERENCES
where owner = 'VAZEP';

And drop Sql Tuning task associate with STS(from above query)

DBMS_SQLTUNE.DROP_TUNING_TASK(task_name => 'RNM_TT');

Then Drop STS

exec dbms_sqltune.drop_sqlset('STS_BSZVN56GN9RWJ');