Specifications

Operat ion Page 61
earlier stages.
Both dump and load operate similarly from the higher level's
perspective. They are invoked with a Dump-self or Load-self function
and checked for completion with the matching poll function. The poll
function returns a state that depends on the progress being made so
that the high level can decide to abort and restart or whatever else
it deems appropriate.
Both dump and load have a special function available on multiaccess
channels. This function allows them to select an assistant from the
dump/load assistance multicast group. The initial request message is
first sent to the multicast address. The first Assistance Volunteer
message responder is selected as the assistant and the operation
proceeds from there the same as for a point-to-point channel. The
initial request is sent via the Must-transact function. During this
stage of the operation, the poll function returns a "requesting"
state.
4.2.2.1 Dump Operation
The first stage is to get the dump started with a Must-transact of a
request dump service message. This succeeds when a request memory
message is received. During this stage, the poll function returns a
requesting" state. On success, proceed to the next stage.
The second stage is the actual dump. During this stage, the poll
function returns an "in-process" state.
A dump data message is sent
in response to each request memory message.
A failure on a transmit
or a receive terminates the operation with a failure or receipt of any
other message.
A timeout on a receive or the receipt of a dump
complete message terminates the operation with success.
4.2.2.2 Load Operation
The first stage is to load a secondary loader program with a Transact
of a request program. This succeeds when a memory load with transfer
address is received and started. The message must contain an entire
secondary loader. Note that a primary loader accepts only a secondary
loader: it does not use the assistance volunteer function.
The second stage is to load a tertiary loader program. The first
segment is obtained with a Must-transact of a request program message.
Subsequent segments are obtained with a simple transmit of a request
memory load
message. The request memory message
is used to
acknowledge the successful or failing storage of the previous memory
segment and either requests the same one again or the next one. The
load is completed by receipt of a memory load with transfer address.
The program loaded must be a tertiary loader.