Kees Vernooy wrote: -snip- >Scott, > >I can't access the post in the archives, maybe this link requires >administrator functions? I have not been able to find it through normal >searces for ATS STAR. -snip-
I'm not an expert on LISTSERV functions, but I had to join the IBM-MAIN-ARCHIVES list to be able to see the archives. I'll copy the pertinent parts of the post here: --------------------------------------------------------- Subject: Re: Sharing tape drives...ibm replacement for mia? From: Scott Fagen <[EMAIL PROTECTED]> Reply-To: IBM Mainframe Discussion List <[email protected]> Date: Wed, 20 Feb 2002 11:27:24 -0600 Content-Type: text/plain -edit- ATS Star - is shipped with base z/OS. - is based on the use of the AS (auto switchable) attribute on VARY and HCD. - also uses assign/unassign to ensure that 'foreign' use of tape drives does not cause tape integrity errors (for example, you could interconnect two ATS Star sysplexes and maintain integrity, you would, however, lose some of the allocation efficiencies inherent in knowing who currently has the drive, what volume is on it, etc.) -edit- As with all things, your mileage may vary. Scott Fagen z/OS Core Technology Design IBM Poughkeepsie --------------------------------------------------------- > >One of the advantages of the large amount of TS7700 units was the >ability to drop CA-MIA. I'd have qualify your statement with 'it depends'. If you have enough drives so that it is never true that the 'lazy' process for reclaiming AFH drives causes allocations to fail, then you can eliminate MIA. On the other hand, AFH is a rather heavy-handed mechanism. The sysplex does not really know which devices in that state can be reclaimed and attempts are made periodically to do so. In the interim, if no drives are available for an allocation (because all candidates are either in use or AFH at the time of the request), then that request will go into recovery allocation. > >With the AFH situation, I am referring to a situation where a system >outside the sysplex has a unit assigned. As I understand ATS STAR now, >the status of units is available through XCF messaging within the >sysplex, so the known AFH units will be lower in the list. However, if a >unit is assigned by a system outside the sysplex, allocation will only >notice this when it selects an apparently free unit, tries to Assign it >and discovers AFH. Will this allocation go and find another unit or will >it wait until the AFH unit becomes available again? Ah, I understand the question now - it will try another unit. The unit is not considered allocated until the ENQ on the device is held and the device is ASSIGNed. This is specifically where MIA is superior to ATS Star. Since the MIA-'plex' scope includes all the systems using the tape drives, there is no chance for a drive to be discovered to be in an AFH state. It's either available or unavailable. >The latter case is not acceptable for production systems and this is my >concern. > >Paragraph Migration Issues Customers Can Experience of apar II13666 more >or less describes the situation where units can be assigned by an >IEFAUTOS systems and ATS STAR systems and this seems similar to units >being allocated by two ATS STAR Sysplexes. Scott Fagen Enterprise Systems Management ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: GET IBM-MAIN INFO Search the archives at http://bama.ua.edu/archives/ibm-main.html
