Data

Data messages carry both inbound and outbound data between the application and the local node on all three connections. See Data Flow for a detailed description of outbound and inbound data flows.

The Data message flows from the node to the application and from the application to the node. It is used with both the SSCP and the PLU connections.

struct Data {
    PTRBFHDR  nxtqptr;
    PTRBFELT  hdreptr;
    CHAR      numelts;
    CHAR      msgtype;
    CHAR      srcl;
    CHAR      srcp;
    INTEGER   srci;
    CHAR      destl;
    CHAR      destp;
    INTEGER   desti;
    CHAR      dfhdr.fhackrqd;
    CHAR      dfhdr.fhpad1;
    INTEGER   dfhdr.fhmsgkey;
    CHAR      dfhdr.fhflags1;
    CHAR      dfhdr.fhflags2;
    INTEGER   dfhdr.fhpad2;
    INTEGER   dfhdr.fhpad3;
    INTEGER   dfhdr.fhseqno;
}; 
 

Element

struct Data {
    PTRBFELT   hdreptr->elteptr;
    INTEGER    hdreptr->startd;
    INTEGER    hdreptr->endd;
    CHAR       hdreptr->trpad;
    CHAR[268]  hdreptr->dataru;
}; 
 

Members

nxtqptr

Pointer to next buffer header.

hdreptr

Pointer to buffer element.

numelts

Number of buffer elements.

msgtype

Message type DATAFMI (0x20).

srcl

Source locality.

srcp

Source partner.

srci

Source index.

destl

Destination locality.

destp

Destination partner.

desti

Destination index.

dfhdr.fhackrqd

Acknowledgment required indicator

NOACKREQ (0x00)
ACKREQ (0x01)

dfhdr.fhpad1

Reserved.

dfhdr.fhmsgkey

Message key.

dfhdr.fhflags1

Application flag 1.

dfhdr.fhflags2

Application flag 2.

dfhdr.fhpad2

Reserved.

dfhdr.fhpad3

Reserved.

dfhdr.fhseqno

Sequence number.

Element

hdreptr–>elteptr

Pointer to buffer element.

hdreptr–>startd

Start of data in this buffer element:

Non-LUA: 13, or 10 for second and subsequent segments of outbound segmented RUs.
LUA, inbound data: 4 in first element, 13 in subsequent elements.

hdreptr–>endd

End of data in this buffer element.

hdreptr–>trpad

Reserved.

hdreptr–>dataru

Data RU.

Remarks

• The use of the acknowledgment required indicator in both inbound and outbound data acknowledgment protocols is described in Data Flow.
• The use of the application flag fields is described in Application Flags (see note below for LUA).
• The sequence number is undefined for inbound data but contains the corresponding SNA sequence number for outbound data.
• If the application is using the LUA variant of the FMI (see FMI Concepts), the TH and (if appropriate) RH are included in the data, and the startd field points to the TH. The fhmsgkey, fhflags1, fhflags2, and fhseqno fields are undefined and should not be used; the corresponding data from the element should be used instead.