The Transfer Size option allows the client to determine how much
data is transferred on a read request (RRQ).
This is useful for requesting a subnet broadcast of a file. The client
finds the size of the buffer it needs in order to store the file in memory.
Drawing from this block size, the client determines the number of blocks for
the transfer. The number of blocks is helpful information for tracking the
blocks that have been received. You can also use it for the last block acknowledgment
(ACK), which must be sent to terminate a transfer normally. Without the Transfer
Size option, determining the size and the last block of the transfer requires
the client to wait for a block to be received that is smaller than the block
size of the transfer.
Note: For files transferred in netascii mode,
this option might not be as useful if you are converting the data during the
transfer in a way that changes its size. Also, the server might require additional
processing time to determine the transfer size due to conversion of the file
to the appropriate CCSID.