Answer
Both are legitimate, Oracle-created system schemas that specific database functionality depends on, and shouldn't be removed. CTXSYS is created during installation and manages Oracle Text — the underlying full-text search engine — with the ability to view and sync Oracle Text indexes, run the knowledge-base extension compiler, and query Oracle Text's own system-defined views; this is directly relevant to IFS, since IFS's Search Domain / document-content search functionality is itself built on Oracle Text under the hood. MDSYS owns Oracle Spatial objects (Oracle's geospatial data types and functions) — a separate standard Oracle component. Both are needed for the Oracle features they support rather than being optional or IFS-specific additions.