Google Gears: Can the Local Server talk to Oracle db?

Normally, Google Gears uses SQLite, and won't go anywhere near an Oracle database.

However, it does seem possible to modify Gears to have it talk with an Oracle database, but this demonstration doesn't make it look particularly easy.

If you're worried about Google Gears messing with your databases, I don't think you have much to fear. If you want to establish a connection, that screencast might get you started.

(Though Gears now seems deprecated, as Google is moving toward HTML5 APIs that provide similar SQLite-based functionality.)

Right now, it is not possible. The use Gears makes of SQLite is all in-process, so it would be very difficult even to modify Gears to do so.

If Gears implemented WebSockets (which it does not, yet, AFAIK) then one way to talk to an Oracle DB would be to implement in javascript a set of drivers for Oracle, i.e., so that it talked directly as a normal client does.
But this would be mighty difficult, would eat tons of memory and would perform horribly. And, anyway, Google is stopping development of Gears and switching to HTML5.

If you really want to do that, perhaps enabling the Oracle web services in the local installation, so that you can send queries via HTTP, from any javascript AJAX library, would be a better idea. You'd need to solve the cross-site scripting restrictions, though, as you'd be downloading code from elsewhere and then, try to connect to localhost.

In short, no, right now you cannot do that.