Tablespace fragmentation

Hello,

I was wondering, is there any way to check the level of tablespace fragmentation? If bigger tables are compressed in the tablespace, some tablespace extents become free. They can easily be reused by other tables as they grow, but if they don't - tablespace stays highly fragmented. This may increase the backup time drastically.. So I want to know if I need to look at tablespace fragmentation reduction at all.
db2 9.7.0.8 on Linux.

Regards,

Tomas