Just a quick question.... Why not use 'create table as select ...' to copy your tables to the new tablespsace and avoid having to write the data to disk?

Eg.
create table newtable tablespace newdata as select * from oldtable;
drop table oldtable;
rename newtable to oldtable;

Syntax above may be a bit dodgy... it came from the top of my head!

Adam.