Prior to DB2 10, the primary constraint to vertical scalability was virtual storage below the 2 GB bar. DB2 V8 introduced 64-bit support for DB2 control blocks and data areas. DB2 9 for z/OS provided an additional10-15% relief for agent thread usage.
The DB2 10 for z/OS target is that up to 90% of the DBM1 address space and the distributed data facility (DDF) address space will be running above the bar. The result is the ability to run much more concurrent work in a single subsystem and to run from five to ten times more concurrent threads.
For instance, if your configuration and application mix can support 500 concurrent threads on a single subsystem with DB2 9, you can support as many as 5000 concurrent threads on a single subsystem with DB2 10.