IBM 7013 J Series, Operator'S Manual

Page: 39 / 297

Using the System Unit
2-7
The following list explains the uses of the key mode switch positions:
Attention: The Reset/Scroll button is active when the mode switch is in the Normal or
Service position, and pressing the Reset/Scroll button can cause data to be damaged or lost
if the operating system is still running.
OK The Normal Position is used for attended operation, which is the usual or
normal placement of the key mode switch when an operator is present and
in control of the operation of the system unit. The Reset/Scroll button is
active when the key mode switch is in the Normal position. The IPL
proceeds according to the Normal Mode Bootlist.
The Secure position prevents the system from booting. If the system is
already booted, this position does not lock the system console or block
system network communication. It also prevents an autoboot in case of a
system crash or checkstop condition.
When the operating system is up, turning the key to the Secure position
disables the Reset/Scroll button. With the key mode switch in this position,
a passerby cannot accidentally press the Reset/Scroll button and cause a
loss of data.
The Service position is used for attended operation when hardware or
software service is conducted. The Service position activates operating
system console sequences that support error determination (debug) and
storage printout (dump). In the Service position, the system unit attempts to
IPL from the media drive. The IPL proceeds according to the Service Mode
Bootlist.
The key mode switch is also used for the following:
•
To indicate to the diagnostic programs that there is no console available. This is
done by setting the key mode switch from Service to Normal and then back to Service
when a
c31
is displayed on the operator panel display.
•
To start a dump. If the system is booted in Normal mode, a manual dump is started with
the key mode switch set to Service and pressing the Reset/Scroll button. If the system is
booted with the key mode switch set to the Service mode, a dump is started by setting
the key mode switch to Normal and pressing the Reset/Scroll button. If the Reset/Scroll
button is pressed twice, the system reboots.
If there is a problem with the system unit, refer to the Problem Solving Guide and Reference
before setting the mode switch to the Service position or pressing the Reset/Scroll button.
Attention: Do not set the key mode switch from Normal (OK) to Service while the system is
booting. Instead, wait until the boot is completed and then change the mode switch setting.