Prevent use of USERSPACE1

The default tablespace of any users in DB2 is USERSPACE1.

Even if you create a new tablespace and grant a user access to that tablespace, it will use USERSPACE1 first when creating a table (if you did not specify a tablespace).

To prevent the use USERSPACE1 tablespace. revoke the use of this tablespace:
REVOKE USE OF TABLESPACE USERSPACE1 FROM PUBLIC