Pathway/iTS SCREEN COBOL Reference Manual (G06.24+, H06.03+, Pathway/iTS 1.0+)

Procedure Division
Compaq NonStop™ Pathway/iTS SCREEN COBOL Reference Manual—426750-001
6-108
USE FOR TERMINAL-ERRORS Statement
irrecoverable. It differs in this respect from the USE FOR SCREEN RECOVERY
statement that executes its declaratives procedure only after the terminal is suspended
and resumed.
If an irrecoverable terminal I/O error occurs and the program does not contain a USE
FOR TERMINAL-ERRORS statement, the program suspends.
If a program contains a USE FOR TERMINAL-ERRORS statement and an
irrecoverable terminal I/O error occurs, the TCP attempts screen recovery automatically
at the next screen operation, unless a DISPLAY RECOVERY statement is executed
successfully before the next screen operation. The next screen operation need not be in
the Declaratives section for the TCP to perform the automatic screen recovery.
The following SCREEN COBOL statements add data to the terminal buffers and thus
could cause an irrecoverable terminal I/O error:
ACCEPT DISPLAY
CLEAR INPUT RECONNECT MODEM
DISPLAY BASE RESET
DISPLAY OVERLAY SCROLL
DISPLAY RECOVERY TURN
For programs operating in conversational mode, an irrecoverable terminal I/O error can
be associated directly with one of the statements listed. For programs operating in block
mode, the error might not result directly from one of these statements.
In block mode, output data is buffered and an irrecoverable terminal I/O error occurs
only when data is actually written to or read from the terminal. A number of input or
output statements could be executed before the buffer fills or some other action forces an
actual write to the terminal. In block mode, actual terminal writes occur in the following
situations:
•
When the terminal buffer is full
•
Before executing an ACCEPT statement
•
Before executing statements such as DELAY, SEND, or CALL
If an irrecoverable terminal I/O error occurs and you have included a USE FOR
TERMINAL-ERRORS procedure in your program, the TCP performs the following
actions:
1. Sets the TERMINATION-SUBSTATUS special register to the appropriate file-
system error code
2. Sets the PW-TERMINAL-ERROR-OCCURRED special register to 1 (otherwise, it
is set to zero)
3. Executes the declaratives procedure immediately following the USE FOR
TERMINAL-ERRORS statement
4. Resumes execution at the statement immediately following the statement during
which the I/O failure occurred
If an error occurs in the declaratives procedure itself, the TCP sets the special registers
PW-TERMINAL-ERROR-OCCURRED to 1 and TERMINATION-SUBSTATUS to the