it's very difficult to help you with the data you're giving. You just write you've issued "SELECT COUNT(*) ..."
I would start checking the system:
- how big are your bufferpools
- did you update the statistics for the table(s) involved?
- do you use different disks for logs and for data?
- and, and, and ...
- do you have an index defined? (DB2 can use it for count(*))
- how many containers did you define for your table? are these containers spread over many disks? how did you define prefetch
- and, and, and...
My suggestion: just google for "DB2 performance optimization", and you'll find lots of tips. Got some concrete question? post it here.