how may i quickly increase the size of columns with millions of rows

Hi

how may i quickly increase the size of columns with millions of rows

alter table ICT_EMAIL_ADDR modify EMAIL_ADDR VARCHAR(75);

this is the tables

SQL> desc ICT_EMAIL_ADDR

Name                                      Null?    Type

----------------------------------------- -------- ----------------------------

ID                                        NOT NULL NUMBER

EMAIL_ADDR                                NOT NULL VARCHAR2(50)

CREATED_BY                                NOT NULL VARCHAR2(30)

UPDATED_BY                                NOT NULL VARCHAR2(30)

CREATED_ON                                NOT NULL TIMESTAMP(6)

UPDATED_ON                                NOT NULL TIMESTAMP(6)

the tables has 31 millions rows

i was thinking to create an index on EMAIL_ADDR

Please give me your inputs

Jesus