parallel database with a single wordpress site

It is possible, but you’ll want to look at MySQL replication and failover. Doing this is something that’s pretty involved and will require someone that knows database management as well as network administration.

please elaborate the process..

Well, there’s three choices.

1. Pay a DB management company to do it for you
2. Hire your own Database Administrator that can do it
3. Spend somewhere around 2 years learning it all for yourself

This sort of thing is not for novices, or even mid-level programmers. It’s really not a programmer thing at all. Database administration at that sort of level is a very specialised field, and requires a lot of specialised knowledge. Much more then you can learn from any forum or tutorial.

Running parallel databases is pretty much overkill for anything but very large commercial sites. It can take a team of people to look after it, and the hardware by itself can be anywhere from two servers to multiple data centres.

If all that is too much the best other answer is to keep regular backups and restore from the last known working one if anything does go wrong. It’s cheaper, simpler and something that you’d be able to do now.