Migrate your existing database to AL32UTF8
Any Single Byte Characterset (like US7ASCII, WE8DEC)
In general :
= The DMU tool is considered more user-friendly, can do the conversion without exp/imp and is easier when data needs correction and when downtime is limited.
= Full exp/imp into a new AL32UTF8 DB is noramlly used when migration to a new server/OS or when downtime is not huge issue.
= csscan / csalter (10g/11g) or Alter Database Character Set (8i/9i) / partial exp/imp is normally preferred by people who like to script things and when downtime is limited.
Subsets and Supersets
Current Character Set New Character Set New Character Set is strict superset? US7ASCII WE8ISO8859P1 yes US7ASCII ALT24UTFFSS yes US7ASCII UTF8 yes