Create index ->Updating the table?

First the setup:
Running Oracle 6.0.36, having different tablespaces, say A, B and C. Have an 8 milion row table in tablespace A, have the indexes on that table on tablespace B, and the rollback and temporary segments on tablespace C. Being the only user on that system.

Creating the first index on the table, we say through the monitor that: Of cource the tablespaces B and C should be written to, but also tablespace A was being updated - why? There is only need to read the columns to index?

The funny thing that really puzzles me is that generating the second and third index, nothing was updated in tablespace A.

Can anybody explain this behaviour?

-- 
Martin Jensen,  Dansk Data Elektronik A/S, Herlev, Denmark
E-mail:      ..!uunet!mcvax!dkuug!dde!mj  or  mj_at_dde.DK
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Don't take life too seriously -- you'll never get out if it alive.