Currently there is no automated way to see if segments that are defined in a DBNAME exist. Minor spelling errors or removal of segments mean that a number of errors can occur at run time and the reasons are not always obvious.
I'd like to see the DBTABLE compiler changed to indicate a warning if the segment doesn't exist. Also, I'd like to see (alternately or additionally) IDMSLOOK to issue a warning when segments are missing.
I don't know enough about the run time process but it seems that if the segment doesn't exist processing continues to the next segment. This could also be a candidate for a warning to show a warning if the segment is missing.