An ACTION ROIV request can be valid or not valid. The VTAM topology agent responds to ACTION requests that are not valid with a single negative response (ROER). Valid ACTION requests are processed, but errors can still occur during that processing. The VTAM topology agent can respond to valid ACTION requests with either positive or negative responses. These responses, however, may not be simple single messages; instead, they may involve a series of messages.

A typical positive response to an ACTION is a number of linked-reply ROIV messages followed by a single ACTION response message (RORS). A negative response to an ACTION request can be more complicated; the negative response may take the form of the ROER, or it can be a linked-reply ROIV message that contains specificErrorInfo data, followed by an RORS message.

The determination of which type of error response is used is dependent upon whether any linked-reply ROIV messages with data have been sent. If no linked-reply messages with data have been sent in response, an ROER is used for the error response. If one or more linked-reply messages have been sent in response to this ACTION request, then a linked-reply ROIV containing the specificErrorInfo construct is sent, followed by an RORS response message.