S/390 PartnerWorld for Developers, ITSO/EFS Project EFS Systems on a Linux Base: Additional Topics

52 EFS Systems on a Linux Base: Additional Topics

There is a second exposure and this involves session or connection drops and timeouts. z/OS

does not like to lose its last console. Where there is only one console, this is the last console.

If the last console is lost, z/OS will attempt to use the “hardware console”. With FLEX-ES this

produces output messages through the command line interpreter (that is, a window with the

flexes> prompt). If the z/OS console (a TN3270 session) and the link needed to obtain a

flexescli window are lost, z/OS might not recover (depending on exactly what is happening in

z/OS at the time).

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You can partly avoid this exposure by always starting a z/OS console on the FLEX-ES server,

in addition to another z/OS console at your remote location. If your remote session fails, z/OS

continues to run with its other console. You can then connect (or reconnect) a TSO session

and use the ISPF LOG option to issue commands from your remote machine.

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The next

example illustrates the use of two consoles.

3.10.4 Remote operation with two z/OS consoles

Recent versions of the AD CD-ROM system have two MVS consoles defined. These

definitions are in the CONSOL00 member of PARMLIB and look something like this:

CONSOLE

DEVNUM(700)

ALTERNATE(908)

AREA(10)

AUTH(MASTER)

(more specifications for this console)

CONSOLE

DEVNUM(908)

ALTERNATE(700)

(more specifications for this console)

This defines two consoles at addresses 700 and 908. Both will be MVS consoles if present at

IPL. Either can be varied online as a console later, provided it is not used by VTAM. Later

console additions involving one of these addresses (after IPL) require operator commands.

Only addresses in the active CONSOLxx PARMLIB member can become consoles. The

easiest way to handle additional MVS consoles is to have them online when the system is

IPLed.

There is only one NIP console during IPL.

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The NIP console receives the first few messages

during system startup. There can be multiple NIP consoles defined in the system, but only

the first available one is used. For the AD system we use for our examples, address 700 (if

online at IPL) is the NIP console and the z/OS console. If 3270s at addresses 700 and 908

are both online at IPL, only 700 will be the NIP console but both will be z/OS consoles.

The NIP console might not be needed during a routine IPL. It is needed (that is, the operator

must reply to messages there) if there are duplicate volsers online, or if the monoplex

operation needs to be initialized, or if something else is wrong early in the IPL process. If you

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FLEX-ES can always send messages to the S/390 hardware console because the FLEX-ES console (which

includes S/390hardware console emulation) is a virtual console. The flexescli command provides a connection to

this virtual console. In this case, we assume the remote operator has lost the link to the FLEX-ES machine and can

access neither 3270 interfaces or flexescli interfaces.

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You might even restart your failed z/OS console by using commands through ISPF. See “Restarting the MVS

console” on page 12 for more about this.

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This is the Nucleus Initialization Program (NIP) function, which has control for a short time after the IPL process

starts. The z/OS consoles we mention are also known as MVS consoles or MCS (Multiple Console Support)

consoles. If your normal console is both the NIP and z/OS console (as is the case in almost all the examples in this

EFS series of redbooks), you will see the console screen change format after the first few messages. This is the

point where the ownership of the console goes from NIP to MCS. At that point any additional MCS consoles become

active.