To check the DB2 Size and Capacity execute the following as the instance owner “db2 ‘call get_dbsize_info(?,?,?,0)'”

Dbsize
An output parameter of type BIGINT that returns the size of the database (in bytes). The database size is calculated as follows: dbsize = sum (used_pages * page_size) for each table space (SMS & DMS).

Dbcapacity
An output parameter of type BIGINT that returns the database capacity (in bytes). This value is not available on partitioned database systems. The database capacity is calculated as follows: dbcapacity = SUM (DMS usable_pages * page size) + SUM (SMS container size + file system free size per container). If multiple SMS containers are defined on the same file system, the file system free size is included only once in the calculation of capacity.

Where the the output parameters are denoted with question mark (?), and specify the refresh-window (input parameter) with an integer value (0 means immediately; -1 means the default refresh window of 30 minutes; 15 means 15 minutes, etc).

Screenshot : Db2 Size and capacity