Oracle 11: Change global index to local on huge production table
I found solution making creating index quite faster... (on Oracle 11g works fine)

drop index I_EMPLOYEE_SALARY_T;
create index I_EMPLOYEE_SALARY_T on EMPLOYEE (SALARY, DEPARTAMENT) 
tablespace IDX_TABLESPACE local unusable;


Then I need to rebuild index online choosing partition:

ALTER INDEX I_EMPLOYEE_SALARY_T REBUILD PARTITION partition_name online;


Altering index is much faster because it using different, faster mechanism and data can be accessed much sooner. For example when data for employees (in this example) is partitioned by timestamp. So newer data are more quickly available.