ESL APPC gives you the option of enabling confirmation processing for the APPC conversation, which makes it possible for your program and its partner to exchange notifications that data has been received and processed successfully. Your ESL program optionally enables confirmation processing when it starts the conversation (see the SYNC_LEVEL argument on the APPCStart subroutine).
In addition to enabling confirmation processing at program startup, your program must also request and send confirmation notifications by calling the appropriate subroutines. Any partner program that wants to communicate with an ESL APPC program that has requested confirmation processing must also be started with confirmation processing enabled.