Guardian Procedure Calls Reference Manual (G06.25+)

Guardian Procedure Calls (C)
Guardian Procedure Calls Reference Manual—522629-013
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CHECKMONITOR Procedure
Considerations
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Takeovers and selectable data segments in use
If the stack has never been checkpointed, then at a takeover, the selectable
segment in use at the time of the call to the CHECKMONITOR or CHECKSWITCH
procedure is put into use. No segment is put into use if the segment is not
available; that is, the SEGMENT_ALLOCATE_CHKPT_ or
CHECKALLOCATESEGMENT procedure was not called to allocate the segment to
the backup process, or the SEGMENT_DEALLOCATE_CHKPT_ or
CHECKDEALLOCATESEGMENT procedure was called to deallocate the segment
from the backup process.
Messages
If CHECKMONITOR (or another checkpointing procedure) returns a value indicating
that a takeover has occurred due to a processor failure, the system subsequently
delivers a system message -2 (processor down) to the $RECEIVE file of the new
primary process. This might not be the first message delivered to the new primary
process if other system messages have arrived since the last checkpoint operation of
the old primary.
If CHECKMONITOR returns a value indicating that a takeover has occurred due to the
primary process stopping, the new primary process receives a system message -101
(Process Deletion) on its $RECEIVE file.
For the format of system message -2 (processor down) or -101 (Process Deletion),
refer to the
Guardian Procedure Errors and Messages Manual.