Introduction to Pathmaker

Overview of Pathway
Introduction to Pathmaker and Pathway
067867 Tandem Computers Incorporated 1–23
Figure 1-10 illustrates a series of related transactions.
Figure 1-10. Context-Free Services
Service 1
Service 3
Service 1
Service 3
Server Class A
Requester
Database
End User
Baines #7563 B
Boogle, Jane,
5 Fenz Rd., #2136
Server A Process 1
Server A Process 2
Server A Process 3
010
Baines, Malcolm,
123 Main, #7563...
Service 2
Service 1
Service 3
1
2
3
4
5
6
7
8
9
10
5
Service 2
Service 210
In this example, an end user wishes to list, one at a time, each person whose last name
begins with the letter B. Service 2 contains the code to perform this task; it has been
packaged with two other services (1 and 3) into Server A. Currently, three Server A
processes are running. A step-by-step explanation of two of these related transactions
follows.
First Transaction:
1. The end user types the letter B in the Last Name field on the screen and initiates
the first request by pressing the function key associated with the List By Name
Service.
2. The requester (working with the TCP) invokes Service 2 (the List By Name
Service) by passing the letter B to the Server Class containing server processes that
contain Service 2.
3. Pathway selects the server process best able to handle the request.
4. That server process (Process 3) directs its copy of Service 2 to read the database,
using the letter B as the starting point.