Hi John - again!

At least as of V5R3 you have more compression options - like *MEDIUM and *HIGH - I ran some tests a few years ago and found that *MEDIUM is pretty good without taking too long - *HIGH is awful in terms of time.

*YES is not really very good compression, BTW.

Your mileage will vary, depending on the kinds of objects and how much white space or other repeated characters you have. So there is no good way to predict size of the compressed image - but it will be quite a bit less, generally, than the 100G you are starting with.

SAVFs can be used, too - with the same compression options on the SAV* commands.

HTH
Vern

-------------- Original message --------------
From: John McKee <jmmckee@xxxxxxxxxxxxxx>

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 files?

John McKee


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