In PostgreSQL, I can do something like this:
ALTER SEQUENCE serial RESTART WITH 0;
Is there an Oracle equivalent?
A true restart is not possible AFAIK. (Please correct me if I'm wrong!).
However, if you want to set it to 0, you can just delete and recreate it.
If you want to set it to a specific value, you can set the INCREMENT to a negative value and get the next value.
That is, if your sequence is at 500, you can set it to 100 via
ALTER SEQUENCE serial INCREMENT BY -400;
SELECT serial.NEXTVAL FROM dual;
ALTER SEQUENCE serial INCREMENT BY 1;