W dniu 2010-11-22 17:30, techie well wisher pisze:
IBM has VTFM (which is diligent/copycross, etc). Why do we need this product
or use this product while we can directly intercept and direct
allocations to a particular storage group (such TMMGROUP) with disk volumes,
let's say a dedicated set aside pool from a storage device? With extended
dataclas attribute, the datasets in this group could be really huge (several
gigabytes). To me, this product adds unnecessary complexity. With this, we
don't need PAT (parallel tape access), because all the datasets in this
group are disk datasets, accessible by multiple address spaces/jobs. Pleaset
let me know your thoughts or am I missing something here?
Well... Diligent is emulated tape drive, data physically reside on your
DASD. Potentially the most expensive DASD in your shop.
Advantages: many tape devices (consurrent jobs), simple replication,
fast tape mounts.
Disadvantages: occupies disk, CPU consuming, especially with compression
(zIIP could relieve it), space is constrained by size of your DASD.
TMM is disk cache backed with real tapes.
Advantages: it's free, it fills up (tries to) your tape volumes, quite
easy to set up.
Disadvantages: it may not solve all your needs.
My humble opinion: it's good idea to get rid off the tapes in data
processing with the exception for activities like ML2, backups, dumps
and archive. YMMV, but usually we want to have data on DIRECT ACCESS
Storage Device. Direct access is good.
--
Radoslaw Skorupka
Lodz, Poland
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BRE Bank SA
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Wedug stanu na dzie 16.07.2010 r. kapita zakadowy BRE Banku SA (w caoci wpacony) wynosi 168.248.328 zotych.
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