Any of the following actions results in an attention sequence:
Database-Library issues a dbcancel() command.
An isql user cancels processing while the server is sending results.
An APT program or form issues a closesql command.
A Data Workbench user exits a form while the server is sending results.
When an attention sequence is issued, the process flow is as follows:
Database-Library issues an attention packet to TRS, then discards anything else received until it receives a TDS DONE packet with the attention Ack bit on.
TRS converts the attention packet into a SNA SIGNAL command, issuing an LU 6.2 request-to-send verb. TRS then discards any results received from the mainframe until it receives a TDS DONE packet with the attention Ack bit on.
At the mainframe, the Server Option receives the attention signal and passes it to the Gateway-Library (RPC).
Gateway-Library passes back a return code, indicating TDS_CANCEL_RECEIVED, on all subsequent TDSNDROW, TDSNDMSG, and TDSETPRM calls from an application. Any data associated with TDSNDROW or TDSNDMSG calls is discarded until the application issues a TDSNDDON call.
For details on these calls, see the Mainframe Connect Server Option Programmers Reference for the appropriate programming language. PL/1 and COBOL versions of this guide are available.
When the application issues a TDSNDDON call, Server Option support sends a TDS DONE packet with the attention Ack bit on. This ends the attention sequence.
