EPI applications send 3270 data to CICS® on calls to the following functions.
The format in both cases is the same. The data stream must be a minimum of 3 non-null bytes, representing the AID and cursor address; the sole exception to this is if the AID represents the CLEAR key or a PA key, when the data stream might consist of the AID only. These fields are passed to the CICS transaction in the EIBAID and EIBCPOSN fields of the EIB.
AID |
Cursor address |
Data buffer |
In either case, the transaction ID can be shorter than 4 bytes, being delimited by either another SBA, an ASCII space, or the end of the string.
The contents of the data buffer passed on the start of a CICS transaction are available to the transaction in response to an initial EXEC CICS RECEIVE command.
When the application replies, the contents of the data buffer are available in an unconverted form in response to an EXEC CICS RECEIVE command or converted to a BMS structure in response to an EXEC CICS RECEIVE MAP command.
It is the EPI programmer's responsibility in the latter case to ensure that the data is formatted correctly so that the conversion succeeds.