The key assembly routine that processes a record image to extract key segments and compose key values may return an error condition, SDAT_ERR, if data is not available (say because of a missing or truncated field), or if some other error code if a problem arises such as a lack of Unicode support for a Unicode key. The add record routines properly return an error if a key assembly error occurs, but the rewrite routines simply treated the key error equivalent to a NUL or missing key. This is not expected to be a common occurrence since it generally takes a badly formed record image. The rewrite routines now return an error on a failed key assembly by default. This keyword reverts to the prior behavior.