Eric Chevalier wrote:
However, we were using 2314s attached to these boxes, and I believe there _was_ a hardware RPQ on the drives. Called something like "Airlines Control Buffer", I _think_ the feature allowed the drive to disconnect from the channel while doing a seek. Whatever the details, it was something that became standard on later mainframe drives from IBM.
http://www.garlic.com/~lynn/2008i.html#19 American Airlines http://www.garlic.com/~lynn/2008i.html#34 American Airlines http://www.garlic.com/~lynn/2008i.html#36 American Airlines http://www.garlic.com/~lynn/2008i.html#37 American Airlines w/o the ACP RQP, loosely-coupled operation required reserve/release commands ... which reserved the whole device for the duration of the i/o operation. Actually reserve could be issued and possibly multiple operations performed before issuing the release (traditional loosely- coupled opeation ... locking out all other processors/channels in the complex). since it was logical name locks, there was significant latitude it choosing lock names ... could be very low level like record name ... i.e. cchhr .... or something higher level like PNR. note that while ACP/TPF did a lot of work on loosely-coupled, it took them quite awhile to getting around to doing tightly-coupled multiprocessor support. The result was quite a bit of consternation in the 3081 timeframe ... which originally wasn't going to have a single processor offering. One of the side-effects was that there were a whole bunch of changes that went into vm370 for enhancing TPF thruput in a 3081 environment ... changes that tended to degrade thruput for all the non-TPF customers. Eventually, there was enough pressure, that a 3083 (single processor) was offered ... primarily for ACP/TPF customers. There was another technique for loosely-coupled operation ... originally developed for HONE (avoiding the performance impact of reserce/release but w/o the airlines controller RPQ). HONE was the world-wide, online (vm370-based) sales & marketing support system. http://www.garlic.com/~lynn/subtopic.html#hone The technique was basically a special CCW sequence that leveraged CKD search commands to simulate the semantics of the mainframe compare&swap instruction (but for DASD i/o operation). The US HONE datacenter provided possibly the largest singie system image at the time (combination of multple loosely-coupled, tightly-coupled processor complex) with load-balancing and fall-over across the complex. Later this was extended to geographic distance with replicated center in Dallas and then a 3rd in Boulder. There was then talks with the JES2 multi-access spool people about them using the same CCW technique in their loosely-coupled operation. ---------------------------------------------------------------------- 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
