Clock connection between the files

[Vladimir Nikishkin]

Hello, everyone.

I have a strange situation. I have a file where I track my used time.
I have another file, in which I write a literate-style book. So I
clock-in in the first file, then open the second one and start
working.

Recently I wrote some terrible code which made my second file blow up
in size to 19 Mb, and I had to kill Emacs.

After restarting Emacs, I wanted to clock-in into the dangling clock
in the first file, but when I type C-c C-x C-i, (!) Emacs asks whether
to open the second file, warning that it is large.
The actual message is "File file2.org is large (19.7M), really open? (y, or n)"

How come org knows the connection between the first and the second
file? There are not any references to the second file in the first one
whatsoever.

Thanks everyone.

-- 
Yours sincerely, Vladimir Nikishkin