Thanks for the prompt responses.

I got the idea from the program asking if I wanted to rewrite the current
cache with an older cache which may hold more information.

I think I assumed that you would start the project, then if it had processed
the first 100 links when you stop it the cache would contain information about
these first 100 links.

If you then started a second session it would see that the first 100 links had
been processed then do the next 100. If you then stop it the cache will
contain info about links 100 to 200.


Then when you started a third time it would see from the existing cache that
links 100 to 200 have been processed, but have no info as to links 0 to 100
and so do them again.

If that is not correct and the cache would tell the program that links 0 to
200 had been done, and so on the third session it would begin at link 201,
then I apologise for misunderstanding.