According to HP the following flow is posted below

1. We get a data from production, by
monitoring it using BSM or WebTrends
tool, production data should support
Peak hour or any specific hour
2. In Performance center define a Load Test, then run and analyze it
3. Add production and testing data to one place as PAL report - and
compare it.
4. Tune the Load Test until it will be similar to that data that we(you) get
from production

.