OSI/AS Programming Manual

Sending and Retrieving User Data
APS Procedures Programming Concepts
2–46 056783 Tandem Computers Incorporated
Table 2-15. Maximum Length of User Data for Procedures That Can Send User Data
Procedure(s) Maximum User Data
Length, Session Version 1
Maximum User Data Length,
Session Version 2
APS_DATA_REQ and
APS_TYPEDDATA_REQ_
No limit No limit
APS_ASSOC_ABORTREQ_ 9 bytes ≤ 10240 bytes*
APS_ACTIVITY_DISCARDREQ_ ,
APS_ACTIVITY_DISCARDRSP_ ,
APS_ACTIVITY_INTERRUPTREQ_ ,
APS_ACTIVITY_INTERRUPTRSP_ ,
APS_CONTROL_GIVEREQ_ , and
APS_TOKEN_GIVEREQ_
None ≤ 10240 bytes*
All other procedures that can send user data ≤ 512 bytes* ≤ 10240 bytes*
* For normal-mode presentation and ACSE connections, you can send as much user data as will fit
into a PPDU of the size specified here; the maximum length depends on the encoding. For
session connections, and for presentation and ACSE connections in X.410-1984 mode, you can
send the full amount of data specified, since no encoding is performed.
Table 2-16. Sequence of Procedures to Send User Data
Procedure What You’re Asking OSI/AS
(Preliminaries) See steps following this table.
APS_DATA_REQ_ Send data to remote application.
[ MFM_AWAITIOX_ ] (Nowait) Await completion; check status.
The following steps explain the sequence of procedure calls given in Table 2-16.
1. Before sending data using APS_DATA_REQ_ , you must do the following:
a. Define a user data buffer, as described earlier in this section under “Defining
User Data Buffers.” For a presentation or ACSE connection, encode the user
data as described earlier in this section under “User Data Encoding.”
b. Establish a connection, as described earlier in this section under “Establishing
a Connection.”
c. Obtain the data token (if the connection is half-duplex and you do not already
hold the token), as described earlier in this section under “Tokens.”