SNAX/APN Application Programming Manual

Introduction to SNAX/APN High-Level APIs

SNAX/APN Application Programming Manual—420111-001

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LU-LU Sessions Between Applications and Devices

When the configuration is done, an LU-LU session can be established between the

application process and a device.

The high-level SNAX/APN protocols allow a Tandem application to communicate with

devices on the IBM network as though they were ordinary files residing on a Tandem

system. Applications participate in LU-LU sessions with devices through file-system

procedure calls. However, a remote LU that represents a device can participate in only

one LU-LU session at a time.

In general, the application performs the following functions:

1. Issues a FILE_OPEN_ procedure call to obtain access to a remote LU.

2. Can issue a CONTROL procedure call (operation 11) to make sure that the remote

LU has been started.

3. Issues a READ, WRITE, or WRITEREAD procedure call to the remote LU to begin

the session.

4. Uses file-system procedure calls to handle data transmission, control information,

and error checking during the session.

5. Issues a FILE_CLOSE_ procedure call to terminate the session.

See the Guardian Procedure Calls Reference Manual for more information on the

various procedure calls.

Issue a READ, WRITE, or WRITEREAD procedure call to begin the LU-LU session

before you issue any other procedure calls. If record size is required, the procedure call

FILE_GETINFOBYNAME_ returns the record size for the CRT protocol, or record size

minus 1 for the ITI protocol. If record size is not required, the CRT protocol returns

1920, and the ITI protocol returns 79.