OSI/AS Programming Manual

Sending and Retrieving User Data
APS Procedures Programming Concepts
056783 Tandem Computers Incorporated 2–45
These procedures have the following characteristics:
APS_DATA_REQ_ sends as many bytes of user data as your program can handle, and
it is subject to token restrictions, as described in Section 3.
APS_CAPDATA_REQ_ and APS_CAPDATA_RSP_ can send a limited amount of user
data when activity management is available, but no activity is in progress. You can
call these procedures only if the capability data exchange functional unit is available.
As defined in the session standard, user-data is optional for these procedures.
APS_CAPDATA_REQ_ is subject to token restrictions, as described in Section 3.
APS_TYPEDDATA_REQ_ sends as many bytes of user data as your program can
handle, ignoring any token settings. You can call this procedure only if the typed data
functional unit is available.
Many other procedures that have a principal function other than sending user data
allow you to send user data as an optional parameter. These procedures are listed in
Table 2-14.
Table 2-14. Other Procedures That Can Send User Data
(APS_)
ACTIVITY_DISCARDREQ_* ASSOC_ABORTREQ_ RESYNCRSP_
ACTIVITY_DISCARDRSP_* ASSOC_CONNECTREQ_ SYNC_MAJORREQ_
ACTIVITY_ENDREQ_ ASSOC_CONNECTRSP_ SYNC_MAJORRSP_
ACTIVITY_ENDRSP_ ASSOC_RELEASEREQ_ SYNC_MINORREQ_
ACTIVITY_INTERRUPTREQ_* ASSOC_RELEASERSP_ SYNC_MINORRSP_
ACTIVITY_INTERRUPTRSP_* CONTROL_GIVEREQ_* TOKEN_GIVEREQ_*
ACTIVITY_RESUMEREQ_ EXCEPTIONREQ_ TOKEN_PLEASEREQ_
ACTIVITY_STARTREQ_ RESYNCREQ_
* These procedures can send user data for session version 2 only.
The maximum amount of user data you can send with an APS procedure call depends
on whether you are using session version 1 or session version 2, on which procedure
you are calling, on the layer of your connection, and (for presentation and ACSE
connections) on whether your connection is in normal mode or X.410-1984 mode.
Table 2-15 shows the maximum user-data value permitted for each procedure that
can send user data.
Table 2-16 gives the sequence of procedures needed to send normal data using
APS_DATA_REQ_. The MFM_AWAITIOX_ call must be included for a nowait
connection, and must not be included for a waited connection. The sequence of
procedures is explained after the table.