File segments generated for Vision Version 5 and 4 files can be given customized extensions.
The naming rules described below do not apply to the first data segment. The name of the first segment is set in the same way that the name of any other data file is set. In this discussion, the name of the first segment is referred to as the regular name.
Vision Versions 5 and 4 use two methods to determine the file names of additional index and data segments (after the first segment).
Both methods allow specific generated file names to be overridden.
The first method takes precedence over the second. That is, if circumstances allow Vision to use the first method, it is used. If not, the second method is used.
In both methods, environment variables are used to indicate how Vision is to determine the names of additional segments. You form the names of these environment variables by taking the regular name of the file, converting all the alphabetic characters to upper case, leaving numeric characters alone, and converting all other characters to underscores ("_"). Thus, gl42.dat becomes GL42_DAT. This name is typically suffixed with another string, depending upon which method you are using, as described below. The runtime looks for these variables in the runtime configuration file. Utilities such as vio and vutil look for them in the operating system's environment.