Exchange/SNA Manual

OPEN Procedure
Exchange/SNA System Procedure Calls
5–14 104700 Tandem Computers Incorporated
.<8> Specifies whether the open message is sent to the Exchange/SNA line
server in nowait I/O mode or not.
0 = The open message is sent in wait I/O mode. The open operation is
complete when control is returned to your program.
1 = The open message is sent in nowait I/O mode. The open operation must
be completed by a subsequent call to AWAITIO.
.<9> Must be 0.
.<10:11> Specifies the exclusion mode in which the Exchange/SNA line server is
opened.
0 = Shared access (allowed with only the console subdevice)
1 = Exclusive access (required for printer, punch, and card-reader
subdevices)
3 = Protected access (not allowed)
.<12:15> Specifies whether you want to perform wait or nowait I/O operations
with the subdevice.
0 = Wait I/O operations. I/O operations will complete before control is
returned to your program.
1 = Nowait I/O operations. I/O operations must be completed by a
subsequent call to AWAITIO. The Exchange/SNA line server allows
only one outstanding nowait I/O operation on each subdevice. If you
specify a number greater than 1, an error is returned by the call to OPEN.
If you omit this parameter, the default setting for each bit is 0. This value results
in the following attributes being specified:
Read/write access
The OPEN message sent in wait I/O mode
Shared access
Wait I/O operations
These default values are suitable only if your application’s sole function is to read
from the console.