User`s guide

3. Checks for the presence of the restart parameter block (RPB) in memory. If the RPB is not
found, the warm
start fails. If the RPB is found, then the console subsystem checks to see if it is
valid (see Section 3.3.1.) If the RPB is not valid warm start fails. If the RPB is valid the console
terminal loads the
SP with the address of the RPB plus X200.
4. Loads the AP (GPR C) with a value that indicates the cause of the warm start.
5. Jumps to the location contained in the second longword of the RPB and starts execution of the
operating system restart routine (Section 3.3.2).
If warm
start fails, the console subsystem prints the console terminal message RESTART FAILED and
attempts to cold
start the operating system (Section 3.2).
If the operating system warm starts successfully, it sends a message to the console subsystem, causing the
console to clear the cold and warm start flags.
3.3.1 Restart Parameter Block (RPB)
The RPB (Figure 3-3) is a block of four longwords starting on a page boundary. It contains sufficient data
for the operating system to warm start itself from the point at which either a power failure or software
crash occurred.
The console subsystem performs the following actions with the RPB during a warm start
sequence:
I. Searches through physical memory for a paged, aligned longword
that contains its own address.
2. Compares the first longword to the second longword of the RPB. If these longwords are equal,
the
RPB is not valid, and the warm start fails. However, if these longwords are unequal, the
console subsystem compares the checksum
of the first 31 longwords of the restart routine
against the contents
of the third longword in the RPB. If the checksum is valid, the RPB is
valid.
3. Checks the warm start flag in the fourth longword. If the warm start flag is set, the warm start
fails. If the warm start flag is not set, the console subsystem starts execution of the restart
routine.
PHYSICAL ADDRESS OF THE RPB 0:
PHYSICAL ADDRESS OF THE VMS WARM START ROUTINE 4:
CHECKSUM OF THE FIRST 31: LONGWORDS OF WARM START ROUTINE 8:
I WARM START FLAG (BIT 0) c:
TK-4306
Figure 3-3 Restart Parameter Block (RPB)
3.3.2 Restart Routine
The restart routine attempts to recover from a power failure or software crash by recreating a consistent
software environment.
The restart routine sets the warm start flag to prevent warm start looping by
displaying a
WARM START IN PROGRESS message. It then restarts the operating system. If the warm
start succeeds, the operating system requests the console subsystem to clear both the cold and warm
start
flags.
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