rac@UUNET.UU.NET ("Robert A. Chekaluk") (08/15/89)
Does anyone know the origin of the IBM term "vary," meaning to attach
or detach a device ("Vary the drive on," "Vary the device off") ??@rice.edu:TS04@UKANVM.BITNET (Chuck Nicholas) (08/16/89)
VARY ON doesn't exactly mean "attach". You can vary a unit address online but then must MOUNT a device for that cua.
@rice.edu:jcmorris@MBUNIX.MITRE.ORG ("Joseph C. Morris") (08/17/89)
In article <12734@brunix.UUCP> rac@cs.brown.edu (Robert A. Chekaluk) writes: > >Does anyone know the origin of the IBM term "vary," meaning to attach >or detach a device ("Vary the drive on," "Vary the device off") ?? Plain English: you're telling the system to VARY the status of the device. The MVS command doesn't refer to attaching or detaching the device. The original (OS/360 PCP) command had only two operands: ONLINE and OFFLINE. To bring a device online, you entered: VARY cuu,ONLINE and so forth. Over the years the VARY command has accumulated a number of additional uses, including the control of TP lines; it also generates an artificial device end interrupt for tape and DASD units when ONLINE is specified. The command was ported to VM (some would say that it contaminated VM) when IBM began supporting VTAM in the VM world. Since the concept of attaching and detaching devices exists under VM, there is a relationship between attaching a device to a virtual machine and, if that machine is an MVS intruder or the VTAM robot, the VARY command could be used to tell the vm that it had a new device to play with.
jcmorris@mbunix.mitre.org (Joseph C. Morris) (08/17/89)
In article <12734@brunix.UUCP> rac@cs.brown.edu (Robert A. Chekaluk) writes: > >Does anyone know the origin of the IBM term "vary," meaning to attach >or detach a device ("Vary the drive on," "Vary the device off") ?? Plain English: you're telling the system to VARY the status of the device. The MVS command doesn't refer to attaching or detaching the device. The original (OS/360 PCP) command had only two operands: ONLINE and OFFLINE. To bring a device online, you entered: VARY cuu,ONLINE and so forth. Over the years the VARY command has accumulated a number of additional uses, including the control of TP lines; it also generates an artificial device end interrupt for tape and DASD units when ONLINE is specified. The command was ported to VM (some would say that it contaminated VM) when IBM began supporting VTAM in the VM world. Since the concept of attaching and detaching devices exists under VM, there is a relationship between attaching a device to a virtual machine and, if that machine is an MVS intruder or the VTAM robot, the VARY command could be used to tell the vm that it had a new device to play with.
@rice.edu:LDW@USCMVSA.BITNET (Leonard D Woren) (08/31/89)
I have no idea why, but starting at MVS/XA, the commands to put a CPU or channel path online or offline are no longer part of VARY, but now are part of CONFIG, a command which prior to MVS/XA was basically useless.