MVS Mainframe Console Operation

The following is a review of common commands used to control MVS consoles.

As with any MVS console, customer personnel assign addresses, update MVSCP/HCD, and update the CONSOLxx member of PARMLIB for standard 327x consoles. It is imperative that operations personnel are informed by the customer of the assigned addresses and operational procedures, if they vary from standard console operational procedures. This ensures that the consoles can be properly managed by operations personnel or automation.

Some MVS systems will have “printer” consoles assigned. A printer console does not have a keyboard, and therefore may be designated as an OUTPUT ONLY device. OUTPUT ONLY console device commands are preceded by “O-” (that is, the letter O followed by a dash). For example, to vary a standard (keyboard attached console) online, enter:

V xxx,ONLINE (use this format for I/O consoles)

If the device in question is an OUTPUT ONLY device, enter:

V O-xxx,ONLINE (use this format for OUTPUT ONLY consoles)

If problems occur, try entering the first format of the command. If it doesn’t work, try the second format.

The same syntax applies to OFFLINE commands:

V xxx,OFFLINE (use this format for devices to be used as I/O consoles)

V O-xxx,OFFLINE (use this format for OUTPUT ONLY devices to be used as consoles)

MVS defined consoles (see SYS1.PARMLIB member CONSOLxx) are not active as consoles until they are “varied” into console status. Varying a console ONLINE does not make a SYS1.PARMLIB defined (see member CONSOLxx) console recognizable to MVS as a console. To do this use another form of vary command, as follows (this should only be issued after the device is ONLINE to MVS):

V xxx,CONSOLE (use this format for I/O consoles)

V O-xxx,CONSOLE (use this format for OUTPUT ONLY consoles)

The commands above should be issued once the device is in the ONLINE status. MVS takes care of this during IPL, but console manipulation after IPL requires manual or automated commands (as previously shown).

In addition, certain error situations require additional MVS console commands. The following are a limited set of commands, but are those likely to be most useful in a VCC based environment:

V xxx,OFFLINE,FORCE (use this format for I/O consoles that refuse to come offline with a V xxx,OFFLINE command)

Note: MVS will produce a WTOR to check if you intend to FORCE this device offline. Respond “YES”.

V O-xxx,OFFLINE,FORCE (use this format for OUTPUT ONLY consoles that refuse to come offline with a V O-xxx,OFFLINE command)

Note: MVS will produce a WTOR to check if you intend to FORCE this device offline. Respond “YES”.

Once the console is offline due to one of the prior commands, a standard “V xxx,ONLINE” of “V O-xxx,ONLINE” will not suffice. It is necessary to issue:

V xxx,ONLINE,UNCOND (use this format for I/O consoles that have previously been taken offline with a V xxx,OFFLINE,FORCE command)

V O-xxx,ONLINE,UNCOND (use this format for OUTPUT ONLY consoles that have previously been taken offline with a V O- xxx,OFFLINE,FORCE command)

In certain cases (I/O errors due to cabling problems, etc.), a console (I/O or OUTPUT ONLY) may “back up”. MVS makes the console operator aware of this situation by one or more messages, for example, IEA404A, IEA405E. These messages state that a particular console is reaching or has reached its buffer limit. As a result of this, a number of messages are “queued” to be delivered, but are being “held” by MVS pending resolution of the problem. In this case, as with standard MVS, it is necessary to “relieve” the backup before the system begins to deteriorate, causing undesirable results due to waits, timeouts, and abends. This action must be taken immediately, so that potential problems that could result from this backup are averted.

The simplest action to take is to issue a VARY online (see previous examples) to get the console out of console status. This command returns the device to MVS device online status, and MVS no longer recognizes the device as an MVS console. However, it still recognizes the device as being capable of becoming a console through a VARY console command. The “backup” condition is alleviated immediately, through re-routing or simple elimination of the messages. If the messages destined for the “backed up” console must be “redirected” to a “live console” (one that is currently functioning properly), issue the console redirection command; for example,

K Q,R=nn|name|HC{,L=cc|name)

Where nn is the “id” of the console device to which the “backed up” messages are being routed. In the unlikely event this command is being issued from the “backed up” console itself, the L= keyword and its operand are not required. This situation will never occur in the case of a “printer console” when the printer console is an OUTPUT ONLY device, as there is no keyboard from which to enter commands. MVS consoles have ids; they may or may not have names.

Use the MVS command “D C” to see all the consoles that are currently assigned. Enter this command from the MASTER console, or the console on which the message indicating that a console was “backed up” appeared. The “numbers” in the left-most portion of the line displays are the console ids. The numbers that follow the “/” (if any) are the alternate console ids. These are the ids of the console(s) that will be used to receive messages if the console whose id (to the left of the “/”) fails. At the same time, check the NBUF= value. A number that is in the hundreds or thousands normally indicates a problem, especially if a “backed up” message has appeared. It is the console with the high NBUF= value whose id is required if opting for the “K Q” type recovery. Now, assuming the console that is backed up has an id of 03, and the working console has an id of 01, issue:

K Q,R=01,L=03

The messages that were backed up on console 03 will now be presented on console 01. Earlier, we stated that issuing a VARY ONLINE was an easy escape from the backed up problem. If you didn’t issue the VARY ONLINE command prior to issuing the “K Q” command, try issuing it after the “K Q” command. If a console is backed up, there must be some sort of problem (for example, with a cable or controller). Issuing a VARY ONLINE command causes the console to go “out of service”, and the alternate console (if any) begins to receive the messages originally destined for the out of service console. Issuing the “K Q” command alleviates the problem, but it is likely that manual intervention will be required to fix the problem. If so, the console should be put ONLINE (or taken OFFLINE) until the problem is resolved, ensuring another backup does not occur during problem resolution. Issuing the “K Q” prior to the offline command guarantees that the messages that were backed up are not be lost, assuming the R= console is available.