To restart the sequence at a different number, you must drop and re-create it.
DROP SEQUENCE EDGE21.GMI_SEQ;
CREATE SEQUENCE EDGE21.GMI_SEQ
START WITH 200000
MAXVALUE 999999999999999999999999999
MINVALUE 1
NOCYCLE
CACHE 20
NOORDER;
DROP PUBLIC SYNONYM GMI_SEQ;
CREATE PUBLIC SYNONYM GMI_SEQ FOR EDGE21.GMI_SEQ;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_PRIV;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_RO;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_RW;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_RWD;
DROP SEQUENCE EDGE21.GMI_SEQ;
CREATE SEQUENCE EDGE21.GMI_SEQ
START WITH 200000
MAXVALUE 999999999999999999999999999
MINVALUE 1
NOCYCLE
CACHE 20
NOORDER;
DROP PUBLIC SYNONYM GMI_SEQ;
CREATE PUBLIC SYNONYM GMI_SEQ FOR EDGE21.GMI_SEQ;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_PRIV;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_RO;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_RW;
GRANT SELECT ON EDGE21.GMI_SEQ TO EDGE21_RWD;