You could go down either route.
If you choose to use "Existing Configuration" you will want to go into adminpv.cmd and update the database details (the dbconfigpv.cmd will update brebootstrap.xml, this allows you to connect to the original database but it will still have your old server details that will need updating). This option will maintain all your settings but doesn't update the DB.
If you choose Create a New Configuration - this will update the brebootstrap file AND create the new configuration which will have the correct database details. BUT i would still recommend then going through the adminpv.cmd and checking all other settings in the new configuration compared to the old one and update where appropriate. This option will not maintain your settings but does create the correct database details.
Hope that helps.
Once you have run through dbconfigpv.cmd it will update BREBootstrap.xml file with the new database details.
When you run adminpv.cmd it will look at this and connect to the new database.
After you've logged into adminpv.cmd you will want to update the following:
Configurations->Primavera P6 Configuration->Database->Instance->Driver Class & URL->URL
You might have a slightly different name to 'Primavera P6 Configuration'
You might have more than one Instance[x] under the configuration - check the URL for all of them.
BTW to edit a field either triple click or highlight it and press F2.
I had reconfigured database connection successfully by option "Existing Configuration"
After that i also changed my URL by login to adminpv.cmd.
I had restarted all my services and weblogic.
But still my web client is still showing my OLD database (in advanced button in login page).
I am also able to login to old database.
I'm not sure I understand the problem.
If you're database server name and ip changes, and you have reconfigured P6 to connect to with new server details- surely you are expecting to be able to log in to your original database.
The name you see in the under the Advanced log in is just an Alias that is controlled in the Database section of the P6 Admin App (you can change this to a new value if it helps)