About In-Memory Neighbor Graph Vector Index

The default type of index created for an In-Memory Neighbor Graph vector index is Hierarchical Navigable Small World.

• Overview of Hierarchical Navigable Small World Indexes
  Use these examples to understand how to create HNSW indexes for vector approximate similarity searches.
• Transaction Support for HNSW Indexes
  Hierarchical Navigable Small World (HNSW) indexes are specialized, memory-only structures designed for efficient vector search. Once an HNSW index is created, any subsequent inserts, updates, or deletes (DML operations) performed on the base table will not be reflected in the index.
• HNSW Graph Persistence
  In addition to the previously defined structures used mostly for transaction consistency, a full checkpoint on-disk structure can also be maintained, if enabled, for faster reload of HNSW indexes after instance restart.
• HNSW RAC Duplication
  Learn how Hierarchical Navigable Small World (HNSW) indexes are populated during index creation, index repopulation, or instance startup in an Oracle Real Application Clusters (Oracle RAC) or a non-RAC environment.