"mac_man2005@hotmail.it" <mac_man2005@hotmail.it> writes:
> Robert, so in my example:
> - tapes are stored in different files (one tape per file)
> - you confirm those first blocks are garbage
> - you confirm they could be rewritten with new data
> This means that we can do recycle space using one tape per file. Correct?
No. You could do that if the rate at which you need to write data to
the file is <= the rate at which you extract it. But for what we
are doing, namely merging runs from several tapes into one output run,
it's pretty much guaranteed that you need new space faster than you are
consuming data from any one input tape. It balances out as long as you
keep *all* the tapes in one operating-system file; otherwise not.
regards, tom lane