This configuration variable specifies a format for naming the index segments of a Vision Version 5 file. The configuration variable starts with the file's base name followed by an underscore and the file's extension, all letters in upper case.
Suppose that the regular name of your COBOL file is /usr1/gl.dat. The variable you would use to set the format for naming the file's index segments is GL_DAT_INDEX_FMT.
The variable must be set equal to a pattern that shows how to create the segment names. The pattern shows how to form the base name and how to form the extension for each segment. Part of this pattern is a special escape sequence (such as %d) that specifies how the segment number should be represented. Choices include %d (decimal segment numbers), %x (lowercase hexadecimal numbers), %X (uppercase hexadecimal numbers), and %o (octal numbers).
For example, setting the variable GL_DAT_INDEX_FMT=gl%d.idx would result in index segments named /usr1/gl0.idx, /usr1/gl1.idx, /usr1/gl2.idx, and so forth.
The %d in the value of the filename_INDEX_FMT above is a printf-style escape sequence. Most reference books on the C language contain an in-depth explanation of these escape sequences, and UNIX systems typically have a man page (man printf) that explains them in detail. Here are the basics:
The escape sequence can be positioned anywhere in the file name, including the extension.
See filename_DATA_FMT for details about naming the index segments. Both variables should be set to corresponding patterns.