User manual

Computer Gateway User Manual 4-15 5/96
4.3
4.3 DATA LINK INITIALIZATION MESSAGES
The CG will not start the scheduling of ACPs or perform any of the normal LCN data
exchanges until it has exchanged a set of initialization messages with the host processor.
The CG begins by sending a time-synchronization message (see paragraph 4.2.1). When
the time-synchronization message is echoed back from the host processor, the CG sends a
message that informs the host processor of the type of restart.
For "cold" restarts, the host processor must restore the CG's database by sending down
any CG-resident Internal DDTs and reconnecting ACPs to their ACIDPs. It then must send
a message indicating that all initialization procedures are complete. For "warm" restarts,
the host processor must ensure agreement between its database and that of the CG before
indicating that the initialization is complete. See paragraph 5.5 for additional information
on the message sequences involved in moving from initialize state to normal operation.
4.3.1 CG Restore
This message originates at the CG and informs the host processor that the link is to be
restarted. Message content informs the host processor of the restart type, which is either
Cold Restart—The CG has been reloaded (initial startup or recovery from a CG failure)
Warm Restart—The CG has not been reloaded (recovery from host processor or data
link failure)
Header information: Word 1—Transaction Code = 43
Word 2—Number of Words = 2
Word 5—CG Identifier = 1
Word 6—Host Task Identifier = RS
Message format: Word 1—Restart type (integer) 1=cold restart
2=warm restart
Word 2—Startup-message number (integer) that is compared with
the returned message in case of multiple restart attempts.
Use information: If the CG has been reloaded, the host processor must retransmit
any data necessary to bring the CG database current with that in
the host processor.
Note that the CG may be reloaded from a current checkpointed file
and, therefore, may already match up with the host computer's
database.