hash Switch

The hash switch lets you transfer files that exist on the destination system only if they have different hash codes on the source and destination systems (indicating that their contents are different). Files that don't already exist on the destination system will always be transferred.

The hash switch can be used with these file transfer commands:
 

transmit and receive    ztransmit and zreceive

Note You may not combine the hash switch in a ztransmit or zreceive command with the longernewer, newer, different, nodelete, or append switches.