General question on index compression and performance

Hello,

I would like to know if index compression can have *negative* performance impacts
to applications.

The background is this:
On thursday 13th I reorganized some indexes which the COMPRESS clause of a certain user schema; I was hoping that besides of space savings on the disks, queries in the schema
may become a little faster by doing this; of course, I did analyze the whole schema right afterwards
(to be clear: it was not SYSTEM).

The COMPRESS clause was used without any following number, and only if the index
had a cardinality/rows ratio that afaik made index compression an appropriate action.
My main reference was Guy Harrisons tuning book.

Today (26th) I am hearing for the first time that users in that schema are recognizing performance loss "since about one week"
with *any* app they are using in that schema. And the apps have not been changed
.
On the other hand, most of the users do not *dare* to call the admins about what is happening ... so it is not very reliable what they say ...

Because I am not too experienced as many gurus here, I would like to ask for an eventual confirmation
about index compression risks,
or if still some more informations are needed to judge the situation. May I have to rebuild the indexes
with NOCOMPRESS again ? It is yet not a "hot issue", I just want to be a little more sure ...

My system:
Oracle EE 8.1.7.3 on AIX 4.3.3 on a Bull server which is now 3 years old ... Oracle Forms & Reports inhouse app on Windows clients

TIA Jan Received on Wed Feb 26 2003 - 02:13:34 CST