SQL*Net allows limited control over the packet sizes via the  
        two parameters 'SDU' and 'TDU'. These control the sizes of the  
        'Session' and 'Transport' layer buffers respectively. 
 
        SDU and TDU sizes are tunable (up to 32K or  32767  bytes) from Oracle7  
        release  7 . 3  onwards. 
 
        TDU is the Transport Data Unit and regulates the size of the sent and 
        read data at the NT layer (the layer that communicates to the actual 
        protocol layer).  Overriding the default TDU size of  32767  bytes is  
        normally not required.  Values for TDU range from  0  to  32767 .  Not 
        setting TDU will set it's value to the default (also the same as 
        setting TDU=0).  A TDU value of 1, for example, will cause the NT layer 
        to read an write only 1 byte of data from, or to, the actual protocol  
        layer.  The NS layer will append all of the data together.  For this  
        reason it is advisable to let SqlNet obtain as much data as it can  
        from the network by using the default values. 
 
        SDU is the Session Data Unit of the NS layer and regulates the size  
        of the sent and read data to the NT layer.  SDU values range from  
        512 to 32767 bytes with a default of 2048 bytes.  To minimize packet  
        header overhead and message fragmentation, set the SDU size as a  
        multiple of the MSS (Maximum Segment Size). When Oracle Advanced  
        Securityencryption is not used, increase the SDU size by one (1). For  
        example, the TCP/IP version 4 MSS on Ethernet is 1460 bytes. Use a  
        multiple of 1460 for the SDU size if encryption is used.  If encryption  
        is not used, increase the SDU size to 1461.  
 
        SQLPlus'  "arraysize"  parameter (a parameter that determines the number 
        of rows fetched per network trip) will obviously play a major role in 
        performance since more fetched rows means more fetched bytes of data.         
 
        For a connection to have an SDU size greater than  2048 , the client and  
        the listener must specify a value for SDU which will then be negotiated  
        to the lowest of the  2  values.