SESSION-LEVEL SEQUENCES

 Oracle Database 12c introduces session-level sequences, which generate sequence values that are maintained independently within each database session:

CREATE SEQUENCE seq_new START WITH 1 INCREMENT BY 1 SESSION;

--session 1:
select seq_new.nextval from dual;
1

--session 2:
select seq_new.nextval from dual;
1

To change this sequence from session level to global level, and vice versa, the following commands are used:

alter sequence seq_new global;

alter sequence seq_new session;