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Data

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Data messages carry both inbound and outbound data between the application and the local node on all connections. For a detailed description of outbound and inbound data flows, see Data Flow.

The Data message flows from the node to the application and from the application to the node. It is used with both the system services control point (SSCP) and the primary logical unit (PLU) connections.

Syntax

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;  
};   
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-logical unit application (LUA): 13, or 10 for second and subsequent segments of outbound segmented request/response units (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 (For more information, see the note that follows 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 function management interface (FMI), the transmission header (TH) and (if appropriate) response header (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. (For more information about FMI, see FMI Concepts.)