Definition
The Integrated File System gives IBM i a directory and stream-file structure similar to Windows or Unix file systems, sitting alongside the platform's traditional library-based object storage. It is actually an umbrella over several file systems, including the root file system, QDLS, QOpenSys, and QFileSvr.400, and it is how IBM i stores things like PDFs, images, logs, and integration payloads that do not fit neatly into a database file.
Buyers researching document management, API integration, or modernization software will run into the IFS constantly, since most modern connectors and web-facing tools read and write through it rather than through traditional libraries.