I´m looking for a faster way to read backwards inside a table.

The Table has more than 400.000 entries.


unique index key bsysid,bclid,order_no Ascending

1. Way

SELECT first 1 order_no FROM ORDER_HEADER WHERE bsysid = 3 AND bclid =
1 AND order_no < 300361 order by order_no desc

Plan
PLAN SORT ((ORDER_HEADER INDEX (ORDER_HEADER_KEY)))

Adapted Plan
PLAN SORT ((ORDER_HEADER INDEX (ORDER_HEADER_KEY)))

------ Performance info ------
Prepare time = 0ms
Execute time = 579ms
Avg fetch time = 579,00 ms
Current memory = 2.402.128
Max memory = 2.484.652
Memory buffers = 8.192
Reads from disk to cache = 8.348
Writes from cache to disk = 0
Fetches from cache = 226.038

2. Way better bad not good.....

SELECT max(order_no) FROM ORDER_HEADER WHERE bsysid = 3 AND bclid = 1
AND order_no < 300361

Plan
PLAN (ORDER_HEADER INDEX (ORDER_HEADER_KEY))

Adapted Plan
PLAN (ORDER_HEADER INDEX (ORDER_HEADER_KEY))

------ Performance info ------
Prepare time = 0ms
Execute time = 500ms
Avg fetch time = 500,00 ms
Current memory = 2.401.612
Max memory = 2.484.652
Memory buffers = 8.192
Reads from disk to cache = 8.348
Writes from cache to disk = 0
Fetches from cache = 226.038


I´ve created an other INDEX like

unique index key bsysid,bclid,order_no Descending

and same combinations of this indexes inside the SQL select
statment, but the result is the same...


My question now has someone a better idea to save this problem
with a better response time ?