If there was sorting involved -- and the only way i see that as possible is if xxx@db-link was actually a view, not a table, and the view query caused sort space to be used -- then the temporary tablespace would be used.

Since it is not, I'm sure that the problem is just that you do not have enough space in the tablespace you are trying to create in. The "temporary" bit id just the table segment before the CTAS is complete -- it is of "temporary" type until the build is complete and it is then changed to "table" type.

Perhaps you need PCTFREE=0 in your storage clause, if you don't want to extend your tablespace.