DDL hanging when different connection is left open

In order to execute a DDL statement  on  a table using a JDBC 
connection, must all other JDBC connections that have performed a read 
query on that table be closed? 

This is what I am seeing:

connection1 performes query: "SELECT * FROM my_table";
connection 2 performs DDL: "ALTER TABLE my_table ADD COLUMN my_col INTEGER";


connection 2 seems to hang unless connection1 is closed (i.e. 
conneciton1.close() ).

This is proving to be a problem when I pool my JDBC connections in my 
application, as connections that are returned to the pool are not 
closed. I tried chaning the transaction isolation levels through JDBC 
but that did not change anything.

Is there a way for me to keep my JDBC connections open, yet still 
perform DDL statements?

Thanks in advance,

-Nathan

-- 
In theory, there is no difference between theory and practice.  But, in practice, there is.

--Jan L.A. van de Snepscheut