Unknown host error message
The FTP client displays EZA1551I Unknown Host: <hostname> if it receives a negative response from the resolver. This occurs when the hostname specified on the FTP command cannot be resolved either by the name server or the local resolution file.
Rule: The FTP client always
uses the z/OS UNIX search order for TCPIP.DATA, even when FTP is invoked
from TSO.
Use the host IP address instead of the hostname on the FTP command, or see Diagnosing resolver problems for information about diagnosing name server problems.