Questions ON Gathering statistics on Index & table

[sumit]

Hello Everyone, few quick questions

(1) Is it advisable gathering statistics on Index & table after creating a NEW index on an OLD large table? Why?
(2) Is it advisable gathering statistics on Index & table if we move any table to KEEP or Buffer pool? Why?
(3) Is it advisable gathering statistics on Index & table if we REBUILD a table in primary key order? Why?
(4) Is it advisable gathering statistics on Index & table after reorganizinf a table based on primary key? Why?

Regards
Sumit

[PAVB]

yes, no, yes (last yes goes for #3 and #4 which are the same).

There is just one reason which is to keep up to date performance statistics which tell Oracle about data and data distribution.

[gandolf989]

5 years ago I worked on an application that inserted and deleted 50,000 rows at a time into a table. They had a way of deciding when to regenerate stats on the table. I removed all stats on that table, since no stats performed better than out of date stats or making people wait to generate stats that will quickly become outdated.

So no, you don't always need to generate stats, just make sure that you don't keep out of date stats.