Size of the Length-Prefix for a Varying Length Item

A variable-length item has a 2- or 4-byte prefix that stores the current length of the item. The size of the prefix is specified by the second parameter of the VARCHAR, VARGRAPH, or VARUCS2 keyword, or by the first parameter of the VARYING keyword. The parameter must be 2 or 4. If you do not specify the prefix size, a size of 2 is assumed if the specified length is between 1 and 65535; otherwise, a size of 4 is assumed. You can specify any prefix size for definitions whose length is between 1 and 65535. A prefix size of 2 cannot be specified for definitions whose length is greater than 65535 since 4 bytes are required to store the length.

For more information, see Variable-Length Character, Graphic and UCS-2 Formats.