Format of user data

As part of the general rules for APPC basic conversations, the user data must be in LL-ID-data format (where LL and ID are each two bytes long), and must follow the attach FMH-5 header.

The CICS® DFHCLS4 program requires the user input data stream to fit into the format shown in Figure 1; if it does not, CICS rejects the data.
Figure 1. Format of user data.
Note:
  1. This is an attach FMH-5 header with its data. Data is passed between the PEM client and the CICS PEM server via GDS variables. For information about GDS, see z/OS Communications Server: SNA Programmer's LU 6.2 Guide.
  2. The GDS record contains GDS data in the format LL-ID-data where:
    • LL, which is two bytes long, is the length of the GDS record, including the LL and ID lengths.
    • ID, which is two bytes long, indicates what the data record represents; for example, X'1221' (sign-on data).
  3. The GDS data record is itself an LL-ID-data record; in this example, a transaction program record (or TP record) where:
    • LL, which is two bytes long, is the length of the TP record including the LL and ID lengths.
    • ID which is two bytes long, indicates the function the TP is to perform; for example, X'FF00' (sign-on) or X'FF01' (signon and change password).
  4. The TP data record is divided up into L-ID-data records (where L and ID are each one byte long). These are known as subfield (or SF records) where:
    • L is the length of the SF record, including the L and ID lengths.
    • ID indicates the subfield being passed; for example, X'01' (userid), X'02' (password), and X'06' (new password).
This figure shows the format of user data for APPC basic conversations.