While a fine moderator of this forum can correct me if I'm wrong, but from what I understand of working with databases, it would make sense that the actual database is "tied up" so to speak whilst you are backing it up.

To understand why, you need to think this through. (Not being rude - just educating)

The database holds content that interacts with something - in this case, information you're presenting on a blog or website application. If you are backing it up, and someone tries to access that database to add new data, do a query, or any other interaction, where is the back-up beneficial if the content is dynamically changing whilst you're backing up? Your backup would be out of date immediately.

I know when working with local programming databases in software application creation, the programs put a lock on the database tables I'm working with so users can't access them while I'm working on them to rebuild, repair, or whatever.

So, I can only make the leap that the databases on the web servers would also do the same when you're backing up. It probably locks down the database from use while the backup is in progress and then releases it when you're backup is finished.

If you are getting a lot of traffic to your site and the lag time is significant to your users, you may want to perform back-ups during a time when the traffic is not so heavy, or schedule the maintenance so that you can put up a notice that the "scheduled maintenance" will be performed during such and such a time and that the site (or database) will be unavailable.

Hope this helps!

Debbie