Mutibyte vs single byte character encoding

We recently migrated from 10.2 to 11.2 which also included migration from single byte encoding characterset to multibyte encoding.

We were doing fine in 11g with new Al32utf8 character set until we started getting multibyte records from our vendors some examples of which include letter 'a' with an umlaut and Euro symbol. Both of these require multibyte storage. One thing more, the nls_length_semantics param is set by default to BYTE.

To make this story short, we did some research and decided to alter BYTE length semantics to CHAR for our varchar columns.

The alter statements looked like:

Alter table abc modify (iid varchar2 (10 char));

We ran the script in our Dev env but got following two errors:

ORA-30556: either functional or bitmap join index is defined on the column to br modified

ORA-01404: Alter column will make an index too large

I googled and also searched on metalink, and most of the forums/notes suggest dropping such indexes, run alter statements and recreate indexes.

Has anyone used any other approach to overcome these errors?

Thanks,
Harinder

--
http://www.freelists.org/webpage/oracle-l