SNAX/APN Application Programming Manual

The SNALU Interface
SNAX/APN Application Programming Manual—420111-001
4-9
SNALU Application as PLU or SLU
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The CANCEL Procedure
A call to the CANCEL procedure cancels a read and/or write operation. It applies to any
outstanding operation (write, read, or write and read) associated with the oldest
uncompleted WRITEREAD call.
•
The CANCELREQ Procedure
A call to the CANCELREQ procedure cancels the specified read and/or write
operation. This call applies to any outstanding operation (write, read, or write and
read) associated with a specific uncompleted WRITEREAD call. The correlation
between a CANCELREQ call and a particular WRITEREAD call is accomplished
by way of a tag parameter in both calls. Like the CANCEL procedure, the
CANCELREQ procedure has meaning only when using nowait I/O.
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The CLOSE Procedure
A call to the CLOSE procedure disables access by the process to the remote LU
(specified by file number). Use this call after terminating the associated LU-LU
session.
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The DEVICEINFO Procedure
A call to the DEVICEINFO procedure obtains the configured LU type and record
size of the specified LU. For SNAX/APN, these are type=14,
subtype={0|1|2|3|4|21}, and record size=4096.
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The FILEINFO Procedure
A call to the FILEINFO procedure obtains error and configuration information about
an opened LU.
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The OPEN Procedure
A call to the OPEN procedure allows access by the process to the specified LU. Use
this call prior to initiating the LU-LU session, as described under Opening an LU
on
page 4-11.
For detailed descriptions of the procedure call syntax, see the Guardian Procedure Calls
Reference Manual.
SNALU Application as PLU or SLU
In an SNA environment, communication between logical units (LUs) occurs within
functional constructs called sessions. A session provides a communications link
between two LUs, one of which acts as the primary logical unit (PLU) and the other as
the secondary logical unit (SLU).
In a SNAX/APN environment, where the Tandem system functions as a node type 2.1,
the SNAX application logical unit (SNALU) interface allows user-written programs to
engage in LU-LU sessions with devices and programs in other SNA type 2.1 nodes.
Note. The CANCEL procedure has meaning only when performing nowait I/O.