Hi,
first, its better to customize a configuration keyword in the dbtune file for each schema (actually, while defining it for each schema you will be needing to reference the data tablespace and the index tablespace in the entries).
second, your current setup would be OK as long as you have sufficient space.
third, always when you create the schema user account in Oracle grant it unlimited quota in data tabelspace and in the index table space:
alter user schema_account quota unlimited on tablespace TS_SCHEMA_DATA_01
alter user schema_account quota unlimited on tablespace TS_SCHEMA_INDEX_01
fourth point, if you want to correct this setup to match your previous setup then create a new fresh schema user account (it will have a different account name) and then setup a DBTUNE keyword for this schema, and then start copying from your OLD schema to the New one through ArcCatalog (copy/paste) your layers.
Hope this helps.
Regards,
Emad