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Failed to connect to MySQL: (1203) User howardkn already has more than 'max_user_connections' active connectionsPath: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: "Stephen Fuld" Newsgroups: comp.arch Subject: Re: ancient disks, Architectural implications of locate mode I/O Date: Sun, 7 Jul 2024 06:23:23 -0000 (UTC) Organization: A noiseless patient Spider Lines: 31 Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Injection-Date: Sun, 07 Jul 2024 08:23:23 +0200 (CEST) Injection-Info: dont-email.me; posting-host="ba103472410feb2a17b6a16ee1809f64"; logging-data="257352"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+nMNJwCirEY0+7Uk5NtnhHU5/fSTUbY9Y=" User-Agent: XanaNews/1.21-f3fb89f (x86; Portable ISpell) Cancel-Lock: sha1:WilOj8N+GrCLpPDwr13dLF/ypvc= Bytes: 2433 John Levine wrote: > According to Stephen Fuld : > >> I believe that's what they did with VSAM. > > > > Agreed in the sense that VSAM replaced ISAM, but, and I am getting > > beyond my depth here, I wasn't aware that PDSs used ISAM. I had > > thought they were a thing unto themselves. Please correct me if I > > am wrong. In any event, PDSs in their original form lasted beyond > > the introduction of VSAM, or the PDS search assist functionality > > wouldn't have been needed. > > A PDS had a directory at the front followed by the members. The > directory had an entry per member with the name, the starting > location, and optional other stuff. The entries were in order by > member name, and packed into 256 byte records each of which had a > hardware key with the name of the last entry in the block. It searched > the PDS directory with the same kind of channel key search it did for > ISAM, leading to the performance issues Lynn described. Yes, I don't disagree with any of that. But I got the impression from your previous posts that IBM had replaced the search key fields of a PDS with some kind of VSAM (i.e. b-tree or such) varient, as they did with ISAM. If that is true I had never heard about it. -- - Stephen Fuld (e-mail address disguised to prevent spam)