Exp/imp no data just structure uses a ton of disk space

Question

I am attempting to migrate a schema from one db instance to another and have run into a problem with disk space. All I want to migrate is the structure. So I am exporting with out the data. Yet the tablespace datafiles grow to a size as if they actually held data. I don't have the disk space for this and would like to know if there is a way around this problem. Also, can anyone provide some insight into why the space would be taken up even though no data is being imported.
I am not a DBA but our DBA suggested I include a compress=n parameter. However, this doesn't appear to solve the issue.
Thanks,
Jason

Answer 1

Go Google for "Databee" and then search their home page for the DDL Wizard
OK, forget that: just go visit http://www.ddlwizard.com/
(It is tricky to see on their home page).
Feed it your row-less export dump files and turn them into a bunch of 'create xxxx' statements. Edit those statements so they aren't asking for stupid INITIAL extent sizes. Run those statements. Then do a standard import using ignore=y. That will get your tables created empty and small and the subsequent import will get all your other schema objects back.
The DBA that suggested compress=n is on the right track: compress=y will mean import will seek to create empty tables as big as the fully-populated table currently is, pre-allocating all the space it thinks the table will eventually need given the amount of data that might, one day, be inserted into it.
Compress=n will seek to create the table with the smallest requested extent size and no more than that: row inserts will make it grow big later on, but that growth is left to happen when it needs to happen.
The only other potential fly in the ointment is, as someone else said, the fact that if you're importing into a tablespace that has been created 'extent management local uniform size 100M', then the mere fact of creating a completely empty table will cause 100M of space to be consumed. You would be much better off making sure your tablespaces are created 'extent management local autoallocate': then you start of with small space allocations and only get bigger when you really need it.