The ISO/ANSI record control word (RCW) is expressed in ASCII characters and is 4 bytes long (see Figure 1). Note that the RCW is different from the code in the IBM® record descriptor word (RDW). The RDW, expressed in binary, is the internal data management equivalent of the ISO/ANSI RCW.
For ISO/ANSI V4 tapes created specifying a CCSID other than ASCII, the RCW will continue to be expressed in ASCII.
Figure 1. Conversion of ISO/ANSI Record Control Word to
D/DB Record Descriptor Word