DB2 tablespace usage query

select cast(tablespace_name as varchar(10)),page_size,usable_pages,used_pages from table (snapshot_tbs_cfg('dbname',-1)) as x where tablespace_type=0

tablespace_type=0 means DMS (Database Managed Space) tablespace. For SMS (System Managed Space) tablespaces, useable_pages always equals used_pages. Substitute dbname with the name of the database.