"Mark Zelden" <m...@mzelden.com> wrote in message news:<9474272146773836.wa.markmzelden....@bama.ua.edu>... > On Mon, 30 Jan 2012 22:35:02 +0000, Martin Packer <martin_pac...@uk.ibm.com> wrote: > > > Because > >of the virtualisation within modern disk controllers robustness favours > >more, smaller. > > > > What 6-9 3390-27 page volumes isn't robust enough? :-) > > And regardless of PAV and where the physical location is on the emulated > DASD, if you put 5 smaller ones on _multiple_ mod-27s, isn't there more of > a chance some of them end up on the same physical disk(s). > > One thing this thread didn't cover are some of the performance > recommendations in the init and tuning guide related to large DASD. > > Recommendation #1, does say to only have one page data set per device.
> and in the z/OS 1.11 manual I have open it even has the updated bars > on the left hand side. > > Writing to contiguous slots and over allocation is mentioned, but unless I > missed it the "old" ROT (and health check) of not having more than 30% > of the slots allocated is not specifically addressed. Certainly with 4K > pages (for the most part) and 3390-27 (or bigger) that 30% ROT doesn't > apply anymore? 50% of a mod-27 is still a helava lot of free slots. > > Mark > -- I discussed the last issue many years ago with Greg Dyck, who then (afaik) was the expert on paging, with regards to 30% free slots on 3390-03 and -09. He stated that simulations still recommended 30% usage, in spite of the helave lot of free slots on the -09. In that same discussion I learned that ASM reserves 2 exposures per pagedataset, so it was no problem putting more than 1 pagedataset on a volume. ASM just ensured 2n-1 PAVs statically assigned to that volume. This seems contradicting with Rec #1 you mention. About health checks: I consider at least 50% of them being writen on a lost Friday afternoon, because of some target to just deliver health checks. Kees. ******************************************************** For information, services and offers, please visit our web site: http://www.klm.com. This e-mail and any attachment may contain confidential and privileged material intended for the addressee only. If you are not the addressee, you are notified that no part of the e-mail or any attachment may be disclosed, copied or distributed, and that any other action related to this e-mail or attachment is strictly prohibited, and may be unlawful. If you have received this e-mail by error, please notify the sender immediately by return e-mail, and delete this message. Koninklijke Luchtvaart Maatschappij NV (KLM), its subsidiaries and/or its employees shall not be liable for the incorrect or incomplete transmission of this e-mail or any attachments, nor responsible for any delay in receipt. Koninklijke Luchtvaart Maatschappij N.V. (also known as KLM Royal Dutch Airlines) is registered in Amstelveen, The Netherlands, with registered number 33014286 ******************************************************** ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to lists...@bama.ua.edu with the message: INFO IBM-MAIN
