In hindsight I rue the decision to set aside both 4xxx and 5xxx addresses. In practice, the low order digit is severely underused. In the beginning I thought that we would need several different 'devices' for each LPAR. Never actually found a need for more than four, 0 - 3. I like Rob Jackson's idea of assigning even/odd numbers for gazinta and gazouta, or ranges like 0 - 7 and 8 - F. Eliminating 5xxx, for example, would free up 4096 addresses for DASD.
OTOH we've never run out of CTC addresses or agonized over which address to use for which device on any LPAR on any CEC. . . J.O.Skip Robinson Southern California Edison Company Electric Dragon Team Paddler SHARE MVS Program Co-Manager 323-715-0595 Mobile 626-543-6132 Office ⇐=== NEW [email protected] -----Original Message----- From: IBM Mainframe Discussion List [mailto:[email protected]] On Behalf Of Ed Jaffe Sent: Wednesday, October 17, 2018 6:10 PM To: [email protected] Subject: (External):Re: CTC conventions On 10/17/2018 4:23 PM, Jesse 1 Robinson wrote: > Just to be clear, a CTC naming convention is not tied uniquely to ESCON or > FICON architecture. We implemented a scheme in the mid-90s under ESCON well > before the advent of FICON. It's still in effect. > > The scheme we adopted (at IBM's suggestion) uses CEC, partition, direction > (in or out for XCF) to construct a four-digit unit number. It has served us > well for decades. The only 'cost' is that lots of addresses are reserved for > CTC. In our case, all 4xxx and 5xxx addresses. I'm sure a more limited scheme > could be utilized, but we connect every LPAR in every CEC to every other LPAR > via CTC, so lots of addresses are utilized. We copied your numbering scheme -- you've posted it here before using the "gazinta" and "gazouta" terminology -- and it works well. If we had more total devices, it might have made sense to fold the scheme down into a single 4xxx address range... -- Phoenix Software International Edward E. Jaffe 831 Parkview Drive North El Segundo, CA 90245 https://www.phoenixsoftware.com/ ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
