Setting the Size of Transfer Units 
Setting the Size of Transfer Units
You must define the size of the send/receive buffer within the application program in accordance with the size of the data to be transmitted. If you have agreed to use different buffer sizes, this may result in data loss if the receiver buffer is too small. The CPI-C implementation in ABAP in R/2 does not allow remaining data to be collected with receive commands. R/3 does not have this restriction.
To achieve optimum performance, the transfer unit size you choose should be as large as possible (parameter LENGTH under
After you have received data, you should check whether the data in the buffer is complete (see parameter DATAINFO under
COMMUNICATION RECEIVE: Receive Data).