Compression can also perform well using compressed indexes. This step performs a deeper analysis of both CPU and IO performance for a select on a table with a compressed index.
Select the actions on this page in order.
SELECT *
FROM customer_address_without_compression
WHERE customer_name = 'SYSCAT PACKAGES'
ORDER BY customer_name
SELECT *
FROM customer_address_with_compression
WHERE customer_name = 'SYSCAT PACKAGES'
ORDER BY customer_name
You can then graph the results for runtime, IO and CPU performance
If you hover your cursor over the bars in the graph you will see the exact sizes of each table.
Just as table compression reduces the IO required for an SQL statement, using compressed indexes compounds the effect. If you want to prove it to yourself, just open the Ad Hoc SQL window, drop the indexes, rerun statistics and rerun the performance test. You should see that the difference in performance between just using compressed table and using compressed indexes as well.