Use options to reduce the time it takes to create the index:

• PARALLEL
• NOLOGGING

SQL> CREATE INDEX rname_idx ON hr.regions (region_name) PARALLEL 4;

WARNING: if you created the index with PARALLEL option 4, then you’ll need to change it back to PARALLEL 1 after the index is created so that it doesn’t use 4 CPUs every time it access the index later!