How do database repository files work?

[Yves M]

I'm looking at storing a vector that's a member of an object. I'd say, at this point, the contents of the vector looks rather volatile.

Ok, so you have a vector that's 1 MB (say), when you change a single byte, do you write the changes immediately to the disk?

I.e how much of the vector has changed between saves? Are the saves frequent (as in automatically if sth changes or every few seconds) or infrequent (as in the user clicks on "Save")?