This is normally the name of a program directory entry in a PDSE. Fast data also permits use of a member parameter with UNIX System Services files. In this context it is treated as an extension of the path name, whether provided in a Path parameter or located through a DD statement. When used this way the member string is simply appended to the path string, and may include subdirectory information. Member is passed as a varying length character string beginning with a two byte binary length field. The length is the number of bytes in the member name, excluding the length field itself.