Envoy ACP/XF Application Programming Manual

File-System Errors

EnvoyACP/XF Application Programming Manual–132179

A-5

Error Recovery and Fault-Tolerant Operation

EnvoyACP/XF uses file-system error codes to inform the application program that the

CPU executing the EnvoyACP/XF communications process failed or that an SCF

command switched control of the line to another CPU. Your application must respond

properly to these error conditions to continue line operation without interruption.

The general recovery procedures for EnvoyACP/XF operations are:

1. When an error indicating a CPU switch is returned, the application process should

issue AWAITIO requests to complete all pending requests for that line. Note that all

such requests complete with an error condition.

2. The application process must reissue any CONTROL requests that were previously

issued to initialize the line and place it in the information-transfer state.

3. If an OPEN, CLOSE, SETMODE, DEFINELIST, CHANGELIST, or CONTROL

request—other than to set the RNR state—is completed with an error indicating a

CPU switch, the application process must reissue the request.

4. If a WRITE, READ, WRITEREAD, or CONTROL request to set the RNR state is

completed with an error indicating a CPU switch, the application must identify a

point at which it can restart information transfer in progress. The application process

can restart the information-transfer sequence only after it has reissued all necessary

CONTROL requests to initialize the line and they have completed.

5. Recovery from error code 66 (device down) requires that you reopen the line(s) and

reissue any SETMODE, DEFINELIST, CHANGELIST, and CONTROL requests

necessary to re-establish both the line configuration and the information-transfer

state. (The application process must reopen the line and reissue the requests because

such requests would be lost if both primary and backup CPUs were to fail.) You can

initiate this recovery only after one of the failed CPUs is returned to service.

30-33 System configuration problem

120-199 Device hardware problem

200-255 Path error, hardware malfunction, or network error