No error recovery is used on the CTC adapter. When running in compatibility mode, the CTC adapter cannot generate any status bits other than attention, busy, channel end, or device end. If any channel errors occur, it is considered proper to signal connection termination to the higher levels. The session must then be restarted by normal initialization protocol.

Prior to the advent of channels that buffer status, attention and busy could only occur if the two systems had lost synchronization. A non-shared 30xx subchannel may cause an attention and/or busy status. This is because the subchannel has already buffered the attention from the other side's I/O request and intends to present it. In channels that do not buffer status, the I/O would have been sent to the CTC adapter, which would have suppressed the attention status and accepted the command. The only option in this case is to reissue the I/O.

On newer, buffered channels, a condition exists where the attention busy status is caused by having another device cause contention. Therefore, the attention busy may occur in normal operation and should not be a termination condition. (See CTC Adapter Attention and Busy Status in System-Dependent Considerations for system-specific handling of this condition.)