Hi,
I am learning to implement range partitioning on AIX 5.3, DB2 V9.1. I created a table and then tried knowing which Tablespace it got associated with:

db2 "CREATE TABLE orders(id INT, shipdate DATE) PARTITION BY RANGE(shipdate) ( STARTING '1/1/2006' ENDING '12/31/2006'EVERY 3 MONTHS)"

From syscat.tables, I found TBSPACEID was -6 but there was no such tablespace with this ID in syscat.tablespaces. How do I know which container the data is going into?

Try:
describe data partitions for table <table name> show detail

You can also query sysibm.sysdatapartitions

Wrong question. Using this syntax you get multiple "tables" in 1 tablespace. The tablespace uses 1 or more containers as usual. Nothing special there.
I suppose you wonder about the spead of "tables" in your tablespace. Now we see that db2girl is capable of giving the right anwer to a wrong question ... wow!