If a user (scott, for example) who is being migrated will have future user entries in a subtree under it, then it makes sense to create a subtree level mapping from this user entry (cn=scott) to a schema. However, the database does not interpret the user to be in the subtree so the mapping does not apply to scott himself. For example, if you are migrating the user scott with the DN cn=scott,o=acme, and you choose SUBTREE as the mapping level when you run the utility, then a new mapping is created from cn=scott,o=acme to the shared schema, but the user scott is not mapped to that schema. Only new users who are created under the scott directory entry are mapped to the shared schema. Consequently, the SUBTREE mapping level should only be specified when user directory entries are placed under other user directory entries, which would be an unusual directory configuration.
If you want an arbitrary subtree user to be mapped to a single shared schema with only one mapping entry, then you must use Oracle Enterprise Manager to create that mapping.
See Also:
"Creating User-Schema Mappings for an Enterprise Domain" for information about using Oracle Enterprise Manager