Pathway/iTS TCP and Terminal Programming Guide

Introduction to TCP and Terminal Application
Programming
Compaq NonStop™ Pathway/iTS TCP and Terminal Programming Guide—426751-001
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Transaction From a Terminal
Transaction From a Terminal
Figure 1-1 illustrates the path of a transaction from a Pathway/iTS terminal, which is
controlled by a SCREEN COBOL program executed by the TCP, to a Pathway server.
For this example, consider a clerk at an order entry office who must update customer
information for account number 1234567.
1. The clerk displays the order screen, a data entry screen, on a terminal. To the
Pathway application, the terminal is defined as object TERM-1.
2. The clerk enters the account number in the appropriate field and requests an update
to customer information by pressing a function key.
3. The requester, which is the TCP interpreting a SCREEN COBOL program, checks
the input data, confirming that the account number has no more than seven
characters. The requester then displays a new screen showing the customer
information as it is currently recorded in the database.
4. The clerk enters the new information (for example, a new customer address) in the
appropriate field and requests that the information be updated by pressing a function
key.
5. The requester checks the input data for validity and confirms that there are no input
errors.
6. The SCREEN COBOL program formats a request message containing the name of
the server class and the data needed by the server to complete its work. The TMF
transaction begins.
7. The SCREEN COBOL program executes a SEND statement, directing the request
message to be sent to the specified server class.
8. If the TCP does not have a link to the specified server class, the TCP asks the
PATHMON process for a link to a server process in the server class. The
PATHMON process replies that a server process is available. If the TCP already
has a link to the server class, this step is not performed.
9. The TCP forwards the request to the server process by using the interproces
communication mechanism of the NonStop™ Kernel operating system.
10. The server process receives and reads the request message.
11. Executing NonStop™ SQL/MP statements in its program, the server process
accesses the database, using the account number as the key, and updates the
specified customer information.
12. The server process formats a reply message verifying the database update and
replies to the TCP using the interproces communication mechanism of the
NonStop™ Kernel operating system.
13. The TCP receives, interprets, and then forwards the reply message to TERM-1. The
TMF transaction ends.The SCREEN COBOL requester program displays a message
on the terminal screen verifying that the specified information has been updated.