Is there any way to assign two tablespaces (TSP1, TSP2) to one User (USER1)? By the tablespace I mean the default Tablespace that is retrieved by DBA_USERS view.

Thanks in advance

as far as I know one user is for one tablespace but if you intend to create indexes or clusters' then you can assign that indexes or clusters' to another tablespace

For big apps we create anymore tablespases (as TSPn, INDn ) and set tablespace in DML command. It is good for administration and optimisation.