Input message format and contents
The input message that an application program receives from a
terminal or another program is in most case containing these fields: the length field, the
ZZ field, the transaction code field, and the text field.
However, if the input message is the result of a Change (CHNG) call that sets the destination of a modifiable alternate PCB to the logical terminal, LU 6.2 descriptor, or transaction code that you specify, then the transaction code field could be absent.
The tables that follow show the message input layouts. The input message field names are in the first row of each table. The number below each field name is the length in bytes that has been defined for that field. The following table shows the format of an input message for the AIBTDLI, ASMTDLI, CBLTDLI, CEETDLI, CTDLI, and PASTDLI interfaces. The message is slightly different for the PLITDLI interface.
| Field Name | Field Length |
|---|---|
| LL | 2 |
| ZZ | 2 |
| TRANCODE | 8 |
| Text | Variable |
| Field Name | Field Length |
|---|---|
| LLLL | 4 |
| ZZ | 2 |
| TRANCODE | 8 |
| Text | Variable |
- LL or LLLL
- The length field contains the length of the input message segment in binary, including LL (or
LLLL) and ZZ. IMS TM supplies this number in the length field
when you retrieve the input message.
For the AIBTDLI, ASMTDLI, CBLTDLI, CEETDLI, CTDLI, and PASTDLI interfaces, define the LL field as 2 bytes long.
For the PLITDLI interface, define the LLLL field as 4 bytes long. The value in the LLLL field is the input message length minus 2 bytes. For example, if the text is 12 bytes, then the fullword LLLL contains a value of 24 bytes. This value is the total of LLLL (4 bytes) + ZZ (2 bytes) + TRANCODE (8 bytes) + text (12 bytes) - 2 bytes.
- ZZ
- The ZZ field is a 2-byte field that is reserved for IMS TM. Your program does not modify this field.
- TRANCODE
- The TRANCODE is the transaction code for the incoming message.
- Text
- This field contains the message text sent from the terminal to the application program. The first segment of a message can also contain the transaction code associated with the program in the beginning of the text portion of the message. Input messages do not have to include the transaction code, but you can provide it for consistency.
The text field’s contents in the input message and the formatting of the contents when your program receives the message depends on the editing routine your program uses.