There are a lot of monitoring table functions available in Db2 to get such an information.
Tablespaces:
MON_GET_TABLESPACE table function
select
sum(case when tbsp_content_type not like '%TEMP' then tbsp_total_pages end * tbsp_page_size)/power(2, 20) data_mb
, sum(case when tbsp_content_type like '%TEMP' then tbsp_total_pages end * tbsp_page_size)/power(2, 20) temp_mb
from table(mon_get_tablespace(null, -2));
Transaction logs:
MON_GET_TRANSACTION_LOG table function
select (total_log_used+total_log_available)/power(2, 20) total_log_mb
from table(mon_get_transaction_log(-2));
Environment routines and views.
You may want to check other functions near these links as well.