Ron,

One of your explanation paragraphs caught my attention so I'm asking out of 
curiosity, for my own benefit.

<your paragraph>

What I find important is there is no data transformation or recall latency:
it is all transparent to the application. You have to read 12 months of
General Ledger files or SMF data sets? The application simply reads them
directly from whatever tier disk the pages happen to be on. You're not
waiting 24 hours for data sets scattered all over myriad ML2 tapes to be
recalled, you don't have to find redundant Primary space to store the
recalled data sets, and there won't be any TMM thrash when they are migrated
again by the next space management cycle. That process is transparent to
z/OS in the way we thought the STK Iceberg would go. Of course all this
dormant data remains replicated with TC and/or HUR while it is being
shuffled around the backstore tiers in both sites - you're not moving any
DFSMShsm traffic across the replication links.

</your paragraph>

The sentence where you said "the application simply reads them directly from 
whatever tier disk the pages happen to be on" intrigues me.  Does the HDS 
scenario you are talking about here use some kind of algorithm to leave this 
kind of data on the level-3 spindles for a certain number of reads (or 
something else like that) or once the page is referenced does it work in the 
background to elevate the pages to higher performance tiers?  

Thanks,

Rex

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