oracle apex truncate collection
BEGIN
IF NOT APEX_COLLECTION.COLLECTION_EXISTS('EMPLOYEE_CL') THEN
APEX_COLLECTION.CREATE_COLLECTION('EMPLOYEE_CL');
ELSE
APEX_COLLECTION.TRUNCATE_COLLECTION('EMPLOYEE_CL');
END IF;
-- Or
APEX_COLLECTION.CREATE_OR_TRUNCATE_COLLECTION('EMPLOYEES_CL');
END;