Are you doing a PowerClient or PowerServer project?  What Chris said is for PowerServer.  But in your title and description you say PowerClient.  PowerClient you would switch the DB same way you do in a traditional client/server application.  PowerClient is just an installer/updater utility for your client/server app.  PowerServer re-architects your app to be n-tier and DB connection happens on the server side (not client side) so then what Chris said is correct for that scenario.

Hi Jagamohan;

1. Create one DB "cache" in PS per DB instance you need your App(s) to access for each customer
2. In the PB App, set the SQLCA.DBParm "cachename=xxxx" at runtime to direct the PS connection to the DB instance you need that customer to use.

Check out the use of the "cachename" parameter in both the PB & PS help.

HTH 

Regards ... Chris