oracle中如何只对一个range分区做索引

oracle表A中月份列为char(6)类型，按月份字段做了range分区。对该表建立local索引，每个分区对应一个索引，索引占了很大的空间。实际上频繁查询的数据就是近几个月的，我现在只想对'P200909'这一个分区做局部索引，其它分区不索引，可否实现？

CREATE TABLE sales_range
(salesman_id NUMBER(5),
salesman_name VARCHAr2(30),
sales_amount NUMBER(10),
sales_date DATE)
PARTITION BY RANGE(sales_date)
(
PARTITION sales_jan2000 VALUES LESS THAN(TO_DATE('02/01/2000','DD/MM/YYYY')),
PARTITION sales_feb2000 VALUES LESS THAN(TO_DATE('03/01/2000','DD/MM/YYYY')),
PARTITION sales_mar2000 VALUES LESS THAN(TO_DATE('04/01/2000','DD/MM/YYYY')),
PARTITION sales_apr2000 VALUES LESS THAN(TO_DATE('05/01/2000','DD/MM/YYYY'))
);

可以..