Really useful for ACK_SYSTEM_FAILURE in PI7.11?

Hi gurus,

Our scenario is idoc2file. You know by default we can see the acknowledment in SXI_MONITOR even when we don't set ACK_SYSTEM_FAILURE to value 1.

After we added the relevant exception in IDXNOALE table, the ack disappeared,whatever the value of ACK_SYSTEM_FAILURE is.

So I'm wondering: what's the use of this parameter? Used in ABAP Proxy ack case?

Thanks in advance.