Spanned record support allows records longer than 255 bytes to be transmitted. For transmission, the records are broken into data segments of less than 256 bytes. The maximum size of a spanned record is 32760 bytes. All segments contain the segment length (SEGL) at the beginning. The total length of the logical record (LRECL) is transmitted following the SEGL in the first segment. (All other segments contain only the SEGL and data.)

The byte used by the SEGL is not included in the SEGL value. The two bytes used by the LRECL are also not included in the SEGL. A sample spanned record transmission is shown in Figure 1.

Figure 1. Spanned Data Record

Figure 2. Spanned Data Record With Carriage Control

Each segment after the first can contain 255 bytes of data. The first may contain a maximum of 253 bytes of data (including the carriage control).

If machine carriage control is used, any CCW opcode may be sent in that record. Store-and-forward systems must forward all CCW opcodes intact. The destination may discard any records that it cannot process.