SMS compression is limited to sequential DASD datasets, but some
utilities (ADRDSSU) uses it internally for tape files. For those
that do, turning off IRDC save cycles in the tape controller.
At 09:12 PM 4/15/2023, kekronbekron wrote:
And an add-on question if I may - zEDC or z15+ on-chip
compression... does this apply only to data heading to disk, or does
it apply for data heading to tape too.
If it applies for data heading to tape also, does that mean there
are 2 levels of compression now - CP's on-chip compression + zstd on
the TS7700?
- KB
------- Original Message -------
On Sunday, April 16th, 2023 at 7:17 AM, John Young
<john.b.yo...@cox.net> wrote:
> Although my post today is probably rhetorical question, I wanted
to find out whether this matters anymore or not.
>
> Back in the late 2000's, IBM developed encryption facilities
within the tape drives, as this is also where compression was being
performed. The idea was that compression of data must occur before
encryption, as encrypted data does not compress well, and obviates
the use of compression.
>
> Nowadays, we've got pervasive encryption on z/OS. As a result,
any data that is backed up (for instance, ADRDSSU/FDR), is already encrypted.
>
> Also, we now have zEDC, to compress data prior to storage,
typically on disk.
>
> To my question: With all the encryption and compression being
performed on disk, to what degree does TAPE COMPRESSION matter anymore?
>
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