On the i5/OS system, files are made up of members. These files are organized into libraries. The convention for naming files is library-name/file-name.
In an ILE RPG program, the name used for a file within the source is specified in positions 7 through 16 in file description specifications. File names can be up to ten characters long and must be unique within their scope, global or local. The EXTFILE keyword can be used to locate the file at runtime; if the EXTFILE keyword is not specified, the same name is used at runtime to locate the file in the library list. For an externally-described file, the EXTDESC keyword is used to locate the file at compile time; if you want the same file to be used at runtime, you can specify EXTFILE(*EXTDESC).
If you do not specify the EXTFILE keyword to locating the file at runtime, or you do not specify the EXTDESC keyword to locate the file at compile time, you can use a file override command to specify a particular name, library or member. See Overriding and Redirecting File Input and Output for more information on file overrides.