I find a partial solution here.

My first choice was this stored procedure, which needs to be called from command line:

db2 'call get_dbsize_info(?,?,?,1)'

Output:

[db2inst1@gina64 ~]$ db2 "call get_dbsize_info(?,?,?,-1)"

Value of output parameters
--------------------------
Parameter Name : SNAPSHOTTIMESTAMP
Parameter Value : 2013-07-04-13.00.05.476704

Parameter Name : DATABASESIZE
Parameter Value : 6993657856

Parameter Name : DATABASECAPACITY
Parameter Value : 5311283195

Return Status = 0

Later I realized that if I would like to use this data in a script, I will need to parse this data. Before doing that I tried the second option:

db2 "select (SUM(total_pages)*4)/1024.0/1024 TOTAL_ALLOCATED_SPACE_IN_GB from table (snapshot_tbs_cfg('dbname',-1)) TBS_SPCE"

Output:

TOTAL_ALLOCATED_SPACE_IN_GB
---------------------------------
                    6.99011230468

This query is more easy to use in a script, but being a lazy person I corrected this query to work without any “customization” for each database…

As you can see, the original query calculate database size assuming that page size is 4K:

... (SUM(total_pages)*4)/1024.0/1024 ...

I changed to this:

... (SUM(total_pages*page_size))/1024.0/1024/1024 ...

The second thing to change is the dbname value:

From:

... table (snapshot_tbs_cfg('dbname',-1)) ...

to:

... table (snapshot_tbs_cfg(CURRENT SERVER,-1)) ...

The final query looks like this:

select (SUM(total_pages*page_size))/1024.0/1024/1024 TOTAL_ALLOCATED_SPACE_IN_GB from table (snapshot_tbs_cfg(CURRENT SERVER,-1)) TBS_SPCE