All BCPii API invocations can experience a communication failure when communicating between the BCPii address space and the support element of the targeted Central Processor Complex (CPC). The calling program receives the HWI_COMMUNICATION_ERROR (101 hexadecimal, 257 decimal) return code when this occurs. One of the output parameters from each service is a Diagnostic Area (referred to as the DiagArea). For the HWI_COMMUNICATION_ERROR return code, a field in this DiagArea that is called Diag_Commerr contains a more descriptive return code from the BCPii communications transport to help pinpoint the cause of the failure.

Below is a partial list of the descriptive communication transport error return codes, along with a suggested action to take.