Clients and servers have to be prepared to reserve memory to store the packages used for communication between them. These packages are called Protocol Data Units, or PDUs. Every PDU starts with an 8-byte header containing a 2-byte, unsigned integer describing the actual size in bytes of the current PDU (including the header itself). Clients and servers must know the maximum size that a PDU sent by the other party could be, and this is called the packet size. The packet size is negotiated at login time.
When connected to ASE 15.0, the ODBC Driver lets the server select the packet size to optimize performance. When connected to an pre-15.0 ASE server, the ODBC Driver uses 512 as the packet size, unless you specify the packetsize property. If you do not want the server to decide the packet size, you need to set EnableServerPacketSize to 0. If you have memory restrictions, you need to set RestrictMaximumPacketSize to a number (in multiples of 512) so that ASE and the ODBC Driver will not negotiate a packet size greater than the one you specified.
