Oracle modify the sequence of values, set cascade delete

Modified sequence of values
the steps of:
modifying increment in this sequence, and then do a select, modify and then increment back.
① -> ② -> ①
① select "layer_id_seq".nextval from dual# query sequence at a value
② alter sequence "layer_id_seq" increment by 1# modify the sequence increase value
③ select "layer_id_seq".currval from dual# query sequence current value (in one session must perform to execute ① ③)

Foreign key cascade delete

ALTER TABLE RECTIFICATION_DOC ADD CONSTRAINT 
FK_rectification_doc_rfeedback
FOREIGN KEY (RFEEDBACK_ID)
REFERENCES RECTIFICATION_FEEDBACK (RFEEDBACK_ID)ON
DELETE CASCADE;