System and method of providing an automatic back-up primary terminal for a cluster of secondary terminals

• US 5,079,740 A
• Filed: 09/21/1989
• Issued: 01/07/1992
• Est. Priority Date: 01/12/1987
• Status: Expired due to Term

• Current Assignee: NCR Corporation
• Original Assignee: NCR Corporation
• Inventors: Watkins, Rex D., Fonner, Susan P., Myers, Gregory L., Patel, Ramesh U.
• Primary Examiner(s): Eng, David Y.
• Assistant Examiner(s): Harrell, Robert B.
• Application Number:
  US07/411,236
• Time in Patent Office: 838 Days
• Field of Search: 364/200, 364/900, 371/7,8.1, 371/8.2, 371/9.1, 371/11.1, 371/11.2, 371/11.3, 371/22.1, 371/22.2, 371/22.3, 371/22.4, 371/22.5, 371/22.6, 370/18, 370/825.05, 370/825.06, 370/825.16
• US Class Current: 714/10
• CPC Class Codes: G06F 11/1662 the resynchronized component or unit being a persistent storage device re-synchronization of failed mirror storage G06F11/2082; rebuild or reconstruction of parity RAID storage G06F11/1008
• CPC Class Codes: G06F 11/20 using active fault-masking, e.g. by switching out faulty elements or by switching in spare elements
• CPC Class Codes: G06F 11/2041 with more than one idle spare processing component
• CPC Class Codes: G06F 11/2097 maintaining the standby controller/processing unit updated initialisation or re-synchronisation thereof G06F11/1658 and subgroups
• CPC Class Codes: G06F 11/2294 by remote test
• CPC Class Codes: G07G 1/14 Systems including one or more distant stations co-operating with a central processing unit data transmission in general H04L; telemetry systems for selectively calling a substation from a main station H04Q9/00

Abstract

A system and method for providing an automatic back-up primary terminal for a cluster of secondary terminals. The primary terminal and the back-up primary terminal are coupled over a communications network to the secondary terminals so that data from the secondary terminals is received simultaneously at both the primary and back-up primary terminals. Either the primary or the back-up primary terminal can function as the active provider of services to the secondary terminals. When either one of the primary terminals becomes inoperative, control is automatically switched to the other one which becomes the active provider of the services. The primary terminal which is the active provider of services keeps a log file (on a disc file) of special data which is to be "backed up" or transferred to the other primary terminal when that other primary terminal becomes operative again. The special data, in the embodiment described, related to price look-up and inventory totals associated with retail terminals.

Claims

1. A method of providing continuous data servicing functions for a plurality of secondary terminals comprising the steps of:

(a) providing a primary terminal and a back-up terminal, said primary terminal or said back-up terminal, when active, being considered a primary provider of said data servicing functions;

(b) coupling said plurality of secondary terminals to said primary terminal and said back-up terminal over a network which enables a message from any one of said plurality of secondary terminals to be received simultaneously at said primary terminal and said back-up terminal;

(c) utilizing a first time-out period and a indefinite order of turning on said first and second primary terminals to determine whether said primary terminal or said back-up terminal is to be active as said primary provider of said data servicing functions;

(d) sending out polling signals over said network by whichever one of said primary terminal or said back-up terminal is said primary provider to enable said plurality of secondary terminals to receive said data servicing;

(e) utilizing a lack of polling signals from said primary provider within a second time-out period for automatically switching to another one of said primary terminal or said back-up terminal to enable said another one to become a next said primary provider of said data servicing functions; and

(f) using said next primary provider from step (e) as the primary provider of said data servicing functions until a failure thereof.

2. The method as claimed in claim 1 in which said utilizing step (c) is effected by:

(c1) listening for polling signals on said network by that one of said primary terminal or said back-up terminal whose said first time-out period has occurred; and

(c2) assuming control as said primary provider if no said polling signals are received within said second time-out period by that one of said primary terminal or said back-up terminal whose said first time-out period has occurred.

3. The method as claimed in claim 2 in which said providing step (a) includes:

(a1) providing said primary terminal with a shorter said first time-out period than said back-up terminal.

4. A method of providing continuous data servicing functions for a plurality of secondary terminals, with one of said data servicing functions being a backing up of totals to be stored;

said method comprising the steps of;

(a) providing a primary terminal and a back-up terminal, said primary terminal or said back-up terminal, when active, being considered a primary provider of said data servicing functions;

(b) coupling said plurality of secondary terminals to said primary terminal and said back-up terminal over a network which enables a message from any one of said plurality of secondary terminals to be received simultaneously at said primary terminal and said back-up terminal so as to enable said totals to be stored at said primary terminal and said back-up terminal;

(c) utilizing a first time-out period and a indefinite order of turning on said first and second primary terminals to determine whether said primary terminal or said back-up terminal is to be active as said primary provider of said data servicing functions;

(d) sending out polling signals over said network by whichever one of said primary terminal or said back-up terminal is said primary provider to enable said plurality of secondary terminals to receive said data servicing; and

(e) utilizing a lack of polling signals from said primary provider within a second time-out period for determining that said primary provider is inoperative and for automatically switching to another one of said primary terminal or said back-up terminal to enable said another one to become a next said primary provider of said data servicing functions;

(f) storing said totals on a log file at a next primary provider of said data servicing functions; and

(g) transferring said totals on said log file from step (f) to said primary provider of step (e) after said primary provider of step (e) again becomes operative to enable said special data to be stored at said primary terminal and said back-up terminal; and

(h) using said next primary provider from step (f) as the primary provider of said data servicing functions until the failure thereof.

5. The method as claimed in claim 4 in which said utilizing step (c) is effected by:

(c1) listening for polling signals on said network by that one of said primary terminal or said back-up terminal whose said first time-out period has occurred; and

(c2) assuming control as said primary provider if no said polling signals are received within said second time-out period out by that one of said primary terminal or said back-up terminal whose said first time-out period has occurred.

6. The method as claimed in claim 5 in which said providing step (a) includes:

(a) providing said primary terminal with a shorter said first time-out period than said back-up terminal.

7. A system comprising:

first and second primary terminals;

a plurality of secondary terminals;

a network coupling said plurality of secondary terminals to said first and second primary terminals to enable a message sent from one of said secondary terminals of said plurality of secondary terminals to be simultaneously received at said first and second primary terminals;

said first and second primary terminals each having a time-out means for generating a first time-out period and a second time-out period;

said first time-out period and an indefinite order of turning on said first and second primary terminals being used by said first and second primary terminals to determine which of said first and second primary terminals is to be an active primary provider of servicing functions to said plurality of secondary terminals and which of said first and second primary terminals is to be a back-up provider of said servicing functions; and

each of said first and second primary terminals also having polling means for sending out polling signals on said network with regard to providing said data servicing functions to said plurality of secondary terminals when either one of said first and second primary terminals is said active primary provider and also for enabling a lack of polling signals by said active primary provider within said second time-out period to be used by said back-up provider to indicate that said active primary provider is inoperative and to enable said back-up provider to thereby become a next said active primary provider of said data servicing functions until the failure thereof.

8. A system comprising:

first and second primary terminals having first and second memory means, respectively, for storing and retrieving data;

a plurality of secondary terminals;

a network coupling said plurality of secondary terminals to said first and second primary terminals to enable a message sent from one of said secondary terminals to be simultaneously received at said first and second primary terminals;

said first and second primary terminals each having a time-out means for generating a first time-out period and a second time-out period;

said first time-out period and an indefinite order of turning on said first and second primary terminals being used by said first and second primary terminals to determine which of said first and second primary terminals is to be an active primary provider of data servicing functions to said plurality of secondary terminals and which of said first and second primary terminals is to be a back-up provider of said data servicing functions; and

each of said first and second primary terminals also having polling means for sending out polling signals on said network with regard to providing said data servicing functions to said plurality of secondary terminals when either one of said first and second primary terminals is said active primary provider and also for enabling a lack of polling signals by said active primary provider within said second time-out period to be used by said back-up provider to indicate that said active primary provider is inoperative and to enable said back-up provider to thereby become a next said active primary provider of said data servicing functions until the failure thereof; and

said first and second primary terminals each having logging means including a log file for keeping totals which are to be stored in both said first and second memory means and also having means enabling a next active primary provider to keep a log of said totals in said log file for later transference to said first memory means or second memory means when a first primary terminal becomes operative again to thereby enable said totals to be stored in both said first and second memory means.

9. The system as claimed in claim 8 in which said first and second memory means comprise first and second hard disc files, respectively, with said log file in each of said first and second primary terminals being part of said first and second hard disc files, respectively.