TABLE A has a column 'userid' as PK. It is generated using sequences.
Everything was fine in our 8i (1 node environment). Now that we migrated to a 4 Node RAC setup, we are getting a PK (unique constraint) error.

This is what is there in the table A:
UserID
...
...
10
11
12
13
14
15
16
17
18
19

When I look at the v$_sequence view, I can see this:

Instace 1
NextVal 5
Highwater 7

Instance 2
NextVal 10
Highwater 12

Instance 3
NextVal 15
Highwater 17

Instance 4
NextVal 19
Highwater 21


The Doc. says that we can use CACHING with 9iRAC-but I don't find that to be the case ?

If I connect to Instance 4, and try to insert into TABLE A using the sequences, everthing is OK, since the next value is not in the table. But if I connect to Instance (1 or 2 or 3) and try to insert into TABLE A using the sequences, it will give a unique constraint, since it is already in the table ?

Can someone please clarify how RAC handles sequences - thanks.