The actual backup process is a bit more complex than that, but Kevin sums it up brilliantly. You can get a very interesting insight if you read the source code of ^DBACK. Do not expect to literally understand all of it though :)
Now to answer your question... Yes it locks every database. More precisely, it locks the *system*, not specific databases. But this is not as bad as it sounds. It just means that the CACHE.DATs will not be written to for a while. This is what ISC calls "quiescing" the system and is actually in the docs, otherwise Support should be glad to help you with it. This can be used in combination with other 'cool tricks', like certain OSs 'snapshot' utilities that can create copies of files in a matter of seconds: you quiesce the DB, run the snapshot and enable updates again. Then you backup the snapshot. As Kevin says this is a minor issue because of the advanced multi-pass stuff. It's quite interesting, IIRC it will automagically determine how many passes it will do depending on current database activity. As far as I can tell I can second John in that it works well and it will probably save you more grief than it can cause. HTH, Ram�n
