Document Invalidation and Garbage Collection

When you remove documents from the base table, Oracle Text marks the document as removed but does not immediately alter the index.

Because the old information takes up space and can cause extra overhead at query time, you must remove the old information from the index by optimizing it in FULL mode. This process is called garbage collection. Optimizing in FULL mode for garbage collection is necessary when you perform frequent updates or deletes to the base table.