Query below can help you find how much space is allocated for LOB data.
Query
select dec(sum(data_object_p_size
            + long_object_p_size
            + xml_object_p_size)/1024.0,20,2) as physical_regular_data,
        dec(sum(lob_object_p_size)/1024, 20,2) as physical_lob_data,
        dec(sum(data_object_l_size
            + long_object_l_size
            + xml_object_l_size)/1024.0,20,2) as logical_regular_data,
        dec(sum(lob_object_l_size/1024), 20,2) as logical_lob_data
from sysibmadm.admintabinfo
where tabschema not like 'SYS%'
Columns
- physical_regular_data - amount of disk space that is physically allocated for the regular data
- physical_lob_data - amount of disk space that is physically allocated for the LOB data
- logical_regular_data - amount of disk space logically allocated for the regular data
- logical_lob_data - amount of disk space logically allocated for the LOB data
Rows
- Query returns just one row
Sample results
Space allocation for LOB and other data types:

 
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                     
                                                                 
                                                             
                                                             
                                                             
                                                             
                                                                 
                                                             
                                                             
                                                                 
                                                             
                                                             
                                                             
                                                             Bart Gawrych
                                                                        Bart Gawrych
                                 IBM Db2
                                                                IBM Db2
                                 SQL Server
                                                                                                SQL Server
                                             Azure SQL Database
                                                                                                Azure SQL Database
                                             MySQL
                                                                                                MySQL
                                             MariaDB
                                                                                                MariaDB