Vista - web service apllication with multiple Database

Hi all,

I want some good advice based on the scenario. the scenario goes below
i have a webservice based application in which multiple clients are
accessing this webservice application
each client have separate database which maintained on the server.
now how can i make faster retrieval of data based on the specific
client mean what is best approach to achieve this functionality.
what will be the best approach to connect to client specific database

any suggestions, please let me know!

Thanks in advance
djdj