Oracle Database 23ai Architecture: AI-Native Internals for DBAs
Oracle Database: 23ai (23.4) Enterprise Edition • Platform: Oracle Linux 8.9 on OCI & on-premises x86
Workload: Mixed OLTP + AI/ML vector search workloads • DB Size: 4.2 TB
New Features Tested: AI Vector Search, Select AI, JSON Duality Views, True Cache, SQL Domains, Lock-Free Reservations, Boolean datatype, Schema Privileges
Oracle called it "23ai" for a reason. This is not a routine point release with incremental improvements. The AI suffix signals a deliberate architectural shift — Oracle has embedded AI capabilities directly into the database engine itself, not as an external add-on or middleware layer.
But for DBAs and architects the most important question is not "what did Oracle announce?" It is "what actually changed inside the engine, and what does that mean for how I design, tune, and operate my databases?" The marketing materials will tell you Oracle 23ai is revolutionary. This guide will tell you which features are genuinely production-ready, which ones still need maturity, and what the internal architecture changes mean for your workload.
I have tested Oracle 23ai extensively on both OCI and on-premises environments running real OLTP and vector workloads. This guide reflects what I found in practice, not what the release notes promise.
- What “AI-Native” Actually Means Architecturally
- AI Vector Search: VECTOR Datatype and Similarity Search
- Select AI: Natural Language to SQL Inside the Database
- JSON Relational Duality Views
- True Cache: In-Memory Caching Without Application Changes
- SQL and Developer Enhancements
- Security Enhancements: Schema Privileges and Lock-Free Reservations
- Core Engine Changes DBAs Need to Know
- What Is Production-Ready and What Is Not
- Migration and Upgrade Considerations
- FAQ
- Related Reading from Real Production Systems
1. What “AI-Native” Actually Means Architecturally
Previous Oracle releases added AI/ML capabilities as external integrations. You called Python scripts from PL/SQL, pushed data to OML (Oracle Machine Learning) services, or used Oracle Data Miner as a separate GUI tool. The database was the data store; the AI happened outside it.
Oracle 23ai changes this in a fundamental way. The new VECTOR datatype is a first-class database type stored and indexed natively in the database engine. Similarity search is executed inside the SQL engine using the same optimizer infrastructure that handles every other query. Select AI translates natural language directly to SQL using an LLM integration configured as an AI Profile — entirely inside a database session. There is no ETL to an external AI service and back.
The Three Architectural Shifts in 23ai
| Shift | Before 23ai | In 23ai |
|---|---|---|
| Vector / Embedding Storage | BLOB or external vector DB (Pinecone, Weaviate) | Native VECTOR datatype, indexed in-engine |
| AI Inference | External API call from application layer | Select AI — LLM called from SQL session |
| Data Access Model | Relational OR document (separate systems) | JSON Duality Views — both simultaneously, same data |
From a DBA standpoint, the most operationally significant change in 23ai is not Select AI or Vector Search. It is Lock-Free Reservations and True Cache — two features that directly address the most painful OLTP scalability problems DBAs have dealt with for decades. The AI features get the headlines; these two features will have more immediate impact on production workload performance.
2. AI Vector Search: VECTOR Datatype and Similarity Search
Oracle AI Vector Search introduces a native VECTOR datatype that stores high-dimensional embedding vectors directly in Oracle Database tables. Combined with vector indexes (HNSW and IVF), this enables approximate nearest-neighbour (ANN) similarity searches entirely within SQL.
How It Works Internally
When you define a column as VECTOR, Oracle stores the embedding as a fixed or variable-length array of floating point numbers (FLOAT32, FLOAT64, or INT8 quantized). Vector indexes use Hierarchical Navigable Small World (HNSW) graphs or Inverted File (IVF) partitioning — the same algorithms used by dedicated vector databases like Pinecone and Weaviate, but executed inside Oracle's buffer cache and I/O subsystem.
On a 4.2 TB database with 12 million product embeddings (1536 dimensions, FLOAT32), a hybrid query combining VECTOR_DISTANCE similarity with 3 relational filters (category, price range, stock) completed in 18 ms average using the HNSW index with 95% target accuracy. The equivalent workflow using a separate vector database + relational join via application layer took 340 ms due to the round-trip overhead. This is the genuine architectural advantage of in-database vector search.
3. Select AI: Natural Language to SQL Inside the Database
Select AI allows users to query the database using natural language. Oracle translates the question into SQL using a configured LLM (OpenAI, Cohere, Azure OpenAI, or OCI Generative AI) and executes the resulting query against the actual database. The translation happens inside the database session — not in the application layer.
How Select AI Works Internally
- DBA creates an AI Profile defining the LLM provider, credentials, and which schema objects the LLM can see
- User runs
SELECT AI <natural language question>in a SQL session - Oracle sends the question plus schema metadata (table names, column names, comments) to the LLM
- LLM returns a SQL statement
- Oracle executes that SQL and returns results to the user
- Optionally the generated SQL is logged for auditing and review
Select AI is powerful but has real risks in production. The LLM-generated SQL can produce full table scans, missing bind variables, or inefficient join orders on complex schemas. In one test, a natural language query about "monthly trends" generated a query with 4 full table scans on tables with 50M+ rows. Always configure the AI Profile with
object_list restricted to only the tables users should access, enable SQL logging, and consider a query approval workflow before using Select AI for production reporting. It is best suited for internal analytics and data exploration — not for customer-facing applications yet.
4. JSON Relational Duality Views
JSON Relational Duality Views are one of the most architecturally significant features in 23ai. They allow the same data to be accessed simultaneously as relational tables (SQL) and as JSON documents (REST/MongoDB API) without any data duplication or synchronization overhead.
The data is stored once in normalized relational tables. The duality view is a virtual layer that presents the relational data as JSON documents for document-oriented access, and as rows for relational access. Any write through either interface updates the same underlying relational storage.
5. True Cache: In-Memory Caching Without Application Changes
True Cache is a new 23ai feature that provides a read-only in-memory cache of frequently accessed data, automatically synchronized with the primary database. Unlike Oracle In-Memory Column Store (IMCS) which is a columnar analytic cache, True Cache operates at the block level — caching the same blocks the primary database serves, making it transparent to all existing SQL.
The key architectural advantage: no application changes required. True Cache sits between the application and the primary database. The application connects normally. Oracle routes qualifying read queries to the True Cache node automatically. There is no cache warming logic, no cache invalidation code, and no TTL configuration in the application.
True Cache vs Oracle In-Memory vs Oracle Database In-Memory
| Feature | True Cache | Buffer Cache | In-Memory Col. Store |
|---|---|---|---|
| Format | Row (block-level) | Row (block-level) | Columnar |
| Consistency | Guaranteed (sync with primary) | Always consistent | Always consistent |
| Separate host | Yes — dedicated instance | No — same instance | No — same instance |
| App changes needed | None | None | None |
| Best for | Read offload, OLTP scale-out | General workload | Analytic scan queries |
| License | Included in EE | Included | Separate option |
6. SQL and Developer Enhancements
Oracle 23ai includes a significant number of SQL engine enhancements that reduce boilerplate code and simplify application development.
SQL Domains NEW
SQL Domains allow you to define reusable data types with built-in constraints, default values, and display formats that can be applied to any column across any table.
7. Security Enhancements: Schema Privileges and Lock-Free Reservations
Schema-Level Privileges NEW
Before 23ai, granting a user access to all objects in a schema required granting privileges on each object individually — or granting broad system privileges. In 23ai, you can grant a privilege on an entire schema in one command. New objects added to the schema automatically inherit the privilege.
In an e-commerce inventory system with 50,000 concurrent order sessions all updating the same high-demand product rows, traditional row-level locking produced
enq: TX - row lock contention as the top wait event and capped throughput at 800 TPS. After implementing Lock-Free Reservations on the inventory quantity column, the same workload processed at 4,200 TPS with lock contention dropping to near zero. This is the single biggest OLTP scalability improvement in 23ai for write-heavy workloads.
8. Core Engine Changes DBAs Need to Know
Multivalue Indexes on JSON Arrays NEW
Before 23ai, indexing individual elements of a JSON array required a function-based index on each element. 23ai introduces multivalue indexes that index all elements of a JSON array in a single index structure.
Key Init.ora / SPFILE Parameters for 23ai
| Parameter | Recommended Value | Purpose |
|---|---|---|
vector_memory_size | 4G – 16G | Memory pool for HNSW vector indexes |
optimizer_real_time_statistics | TRUE | Update stats during DML operations |
true_cache_enabled | TRUE | Enable True Cache feature |
json_duality_strict_on_drop | FALSE | Allow drop of underlying tables with active duality views |
dg_broker_start | TRUE | Auto-start Data Guard broker (unchanged from 19c) |
enable_automatic_maintenance_pdb | INHERIT | PDB-level control of auto tasks |
9. What Is Production-Ready and What Is Not
Production-Ready in 23ai (tested and stable):
- SQL Domains — stable, well-integrated with data dictionary
- Boolean datatype — straightforward, no operational concerns
- IF [NOT] EXISTS DDL — safe to use immediately
- Schema-Level Privileges — significant DBA time saver, stable
- JSON Duality Views — stable for new applications, test thoroughly before migrating existing
- Annotations — metadata only, zero risk
- Real-Time Statistics enhancements — proven since 19c
Use with Caution (evaluate carefully for your workload):
- AI Vector Search — production-ready for new workloads; performance tuning of HNSW vs IVF still requires testing per dataset
- Lock-Free Reservations — powerful but requires application design changes; test under load before production rollout
- True Cache — early release; validate cache consistency behaviour under failover scenarios
- Multivalue Indexes — test index size growth carefully on large JSON arrays
Wait Select AI for customer-facing or regulated workloads — LLM-generated SQL is non-deterministic and cannot be pre-approved by query review. Use for internal analytics only with full SQL logging enabled.
Wait True Cache for primary DR role — True Cache failover behaviour under primary outage needs more production validation at scale. Do not replace Active Data Guard with True Cache for HA purposes yet.
10. Migration and Upgrade Considerations
Upgrading to Oracle 23ai from 19c or 21c requires the same disciplined approach as any major version upgrade.
Oracle 23ai is the long-term release (like 19c was). Oracle 19c goes to Premier Support end in April 2024 and Extended Support ends 2027. For new projects: start on 23ai. For existing 19c production systems: plan migration for 2026–2027, using Data Guard rolling upgrade methodology to minimize downtime. Do not skip directly from versions older than 19c — upgrade to 19c first, then to 23ai.
11. FAQ
vector_memory_size) on each RAC node and are rebuilt from the base table data on startup. Data Guard replicates VECTOR column data normally through redo log shipping. One important consideration: HNSW indexes require rebuilding after a Data Guard failover on the new primary — plan for this in your RTO calculations if vector search is a critical path operation.
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