My question was well answered. I knew that both virtual tape and save files took up space. Obviously, for decent performance, a separate ASP is almost mandatory. What I had wondered was whether multiple processes could be used to speed up backup. I was thinking that critical libraries could be backed up to a SAVF and later transferred to tape with the system being available for users. Short answer is >maybe<, as availability of DASD is still a factor, as I thought surely it would be. Years ago, I wrote a CL that prioritized
the libraries to be backed up. Once the high priority libraries
were safely on tape, other libraries were kept locked and users were allowed back in. As each remaining library was backed up, the lock on
the library was released. That did cut downtime considerably, on
that ancient system. <<SNIP>>
John McKee wrote:
To back up 100G of DASD to virtual tape, would you need 100G of
DASD for the virtual tape? Or possibly a better question: Does
virtual tape utilize data compression, thus not requiring quite as
much space as if data was simply copied disk to disk?
How would the size be calculated?
How does virtual tape compare to using a save file or multiple save