If you purchase DB2 Workgroup Server Edition V9.7 under the Processor Value Unit (PVU) charge metric, you can deploy it on a system which can use a maximum of 64 GB of instance memory, even if the server has more than 64 GB of memory. Starting in Version 9.7 Fix Pack 3a, the instance memory limit has been increased to 64 GB.
For DB2 Version 9.5 or higher, you can deploy DB2 Express Edition on a system with up to 200 VU, and it can use a maximum of 8 GB of instance memory, even if the system has more than 8 GB of memory. You can have multiple instances of DB2 Express Edition, but the combined memory of those instances cannot exceed 8 GB. For example, if you had 2 instances, each instance could only use a maximum of 4 GB of memory.
You can use the instance_memory database manager configuration parameter to specify the maximum amount of memory that the database manager is allowed to allocate from its private and shared memory heaps.