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knowledge-base/ORACLE.en.md
Stanislav Hubacek 3fa11ef0f6 comiiit
2026-06-11 15:27:28 +02:00

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🏛️ Oracle Database

Overview

Oracle Database is a proprietary relational database with the broadest range of enterprise features — RAC clustering, Active Data Guard, partitioning, advanced compression, in-memory options, and Oracle Exadata integration. Dominant in the corporate world, finance, telecommunications, and mainframe ecosystem.

Architecture

Oracle instance + database

Oracle Instance (memory + processes)
  ├── System Global Area (SGA)
  │   ├── Database Buffer Cache
  │   ├── Shared Pool (library cache, dictionary cache)
  │   ├── Redo Log Buffer
  │   ├── Java Pool
  │   ├── Large Pool (backup, parallel)
  │   └── In-Memory Column Store (option)
  ├── Program Global Area (PGA) — per session
  └── Background processes
      ├── PMON (process monitor)
      ├── SMON (system monitor)
      ├── DBWn (database writer)
      ├── LGWR (log writer)
      ├── CKPT (checkpoint)
      ├── ARCn (archiver)
      └── MMON (manageability monitor)

Multitenant architecture (12c+)

Container Database (CDB)
  ├── Root (CDB$ROOT) — metadata, system objects
  ├── Seed (PDB$SEED) — template for new PDBs
  ├── Pluggable Database 1 (PDB1) — application A
  ├── Pluggable Database 2 (PDB2) — application B
  └── Pluggable Database 3 (PDB3) — application C

Each PDB looks like a separate database but shares SGA and background processes. Advantage: higher density, simpler patching (CDB level), resource management per PDB.

Oracle RAC (Real Application Clusters)

Multi-instance architecture — multiple servers access the same storage:

Node 1 ─── Oracle ASM ─── Shared Storage (SAN/NFS)
Node 2 ─── Oracle ASM ─── Shared Storage (SAN/NFS)
Node 3 ─── Oracle ASM ─── Shared Storage (SAN/NFS)
              │
        Cache Fusion (private interconnect)
  • Up to 64 nodes in a cluster
  • Cache Fusion — transfer of dirty blocks between instances via private interconnect (RAC-specific)
  • ASM (Automatic Storage Management) — clustered filesystem + volume manager
  • Service — workload routing (primary, report, batch)

Oracle Data Guard

Mode Protection Latency Use case
Maximum Protection Zero data loss (sync) Highest Critical systems
Maximum Availability Zero data loss (sync, fallback to async) High Enterprise standard
Maximum Performance Async Lowest Remote DR
  • Active Data Guard — standby for reads (reporting, backup) — requires license
  • Far Sync — synchronous write to remote standby via async (compromise)

Oracle Exadata

Hardware+software platform for Oracle DB:

Component Description
Database Servers x86 (Xeon), 2-8× per rack, NVMe, 1.5-6 TB RAM
Storage Servers Total capacity up to 2.7 PB raw per rack
Smart Scan Predicate filtering at the storage layer (instead of DB server)
Smart Flash Cache Multiple caching layers (RAM, Flash, disk)
RDMA over Converged Ethernet Low latency between DB and storage servers

Suitable for: largest OLTP, data warehousing, consolidation.

Key enterprise features

Feature Description Competition
RAC Shared-everything cluster up to 64 nodes MSSQL AlwaysOn FCI (2 nodes)
Active Data Guard Standby for reads, far sync, automatic failover MSSQL AlwaysOn AG, PostgreSQL streaming
Partitioning Range, List, Hash, Composite, interval, reference PostgreSQL (declarative partitioning 10+)
Advanced Compression Columnar, HCC (Exadata), OLTP compression InnoDB page compression, PG TOAST
In-Memory Column store in SGA for real-time analytics PG (no native), MSSQL (columnstore index)
Advanced Security TDE, data redaction, VPD, audit vault, database firewall PG (pgcrypto, pgaudit), MSSQL (TDE, Always Encrypted)
Flashback Querying historical data (Flashback Query, Table, Database) PG (temporal tables via extension), MSSQL (system-versioned)
Sharding System-managed, composite, user-defined MongoDB (native), Vitess (MySQL), Citus (PG)
ASM Clustered filesystem + volume manager VMware VMFS, Windows CSV

Oracle licensing detail

Editions

Edition Metric Price (indicative) Limitations
Oracle Database Standard Edition 2 (SE2) Per core (core factor 0.5) ~$17,500/core Max 16 CPU threads (per server), max 2 sockets, no RAC (only Oracle RAC One), no partitioning, in-memory, compression
Oracle Database Enterprise Edition (EE) Per core (core factor 0.5) ~$47,500/core No limits, all features (RAC, partitioning, in-memory, compression, Advanced Security) — but all as optional licenses
Oracle Database Enterprise Edition (RAC) Per core (EE + RAC option) ~$47,500 + $23,000/core EE + RAC clustering

Optional licenses (options) — EE only

Option Price (indicative / core) Use case
Real Application Clusters (RAC) ~$23,000 Multi-instance cluster
Active Data Guard ~$10,000 Standby for reads, far sync, automatic failover
Partitioning ~$11,500 Range, list, hash, interval, reference, system
Advanced Compression ~$11,500 OLTP compression, HCC (Exadata), JSON compression
Advanced Security ~$15,000 TDE, data redaction, database firewall
In-Memory Database ~$23,000 Column store in SGA for real-time analytics
Database Vault ~$5,750 Separation of duties, multi-tenancy security
Multitenant (EE) Free (since 21c) CDB/PDB — max 3 PDB per CDB in EE without license. Unlimited with Multitenant option (~$17,500)
Spatial / Graph ~$5,750 Geospatial data, property graph
Label Security ~$5,750 Row-level security with classifications

Oracle Cloud (OCI) licensing

Service Model Price Note
OCI Base Database (RDS-like) BYOL or License Included ~$1-5/hour (BYOL cheaper) Single instance or RAC, automatic backup, patching
OCI Exadata Database Service BYOL or License Included ~$5-30/hour (depending on shape) Exadata X9M/X10M in OCI, elastic, full Exadata features
OCI Autonomous Database Per CPU (ECPU) ~$0.50-3.00/ECPU/hour Auto-tuning, auto-scaling, auto-patching
BYOL (Bring Your Own License) Own Oracle license in OCI Infrastructure only Can use existing perpetual license, including support

RAC sizing — license cost

4-node RAC, each node 2× EPYC 9654 (96C) = 192 cores per node
  Core factor 0.5 → 96 Oracle licenses per node
  4 × 96 = 384 Oracle EE licenses

EE: 384 × $47,500 = $18,240,000
RAC option: 384 × $23,000 = $8,832,000
Support 22% annually: ($18,240,000 + $8,832,000) × 0.22 = $5,955,840/year

Tip: For RAC, consider smaller CPUs (e.g., 64C instead of 96C) — license cost often exceeds hardware cost.

Oracle vs PostgreSQL — comparison

Area Oracle PostgreSQL
License Proprietary (per core, ~$17.5k-47.5k/core + 22% support annually) Open source (PostgreSQL license, MIT-like)
RAC clustering Native, shared-everything None (Citus = shared-nothing)
Multitenant CDB/PDB architecture None (schemas per tenant)
Parallel execution Mature (auto DOP, parallel index scan) Good (parallel seq/index scan, join)
Storage management ASM (integrated) OS volume / LVM
Materialized views With refresh on commit, query rewrite No query rewrite
Partitioning 40+ options (interval, referential, system) Declarative (range, list, hash since 10+)
In-memory Columnar in SGA Not native
Standby usage Active Data Guard (read-only, license) Hot standby (read-only, free)
Cloud OCI (Oracle Cloud), AWS RDS, Azure All clouds (native)

Recommendations — where Oracle is better

Area Oracle Competition Why Oracle
License cost (4-node RAC, 384 cores) ~$50M (1st year incl. support) PostgreSQL: $0 Oracle: 22% support annually on license fee
Vendor lock-in High (GoldenGate migration difficult, PL/SQL specific) PostgreSQL: none MySQL and PG have migration tools from Oracle (ora2pg, AWS DMS)
Enterprise OLTP RAC + ASM, zero-downtime patching MSSQL (FCI limit 2 nodes) Shared-everything cluster, transparent failover
Finance / Banking Audit Vault, Database Vault, TDE, VPD PG (pgaudit, row-level security) Compliance certifications (SOX, PCI, GDPR)
Consolidation Multitenant (CDB/PDB) — hundreds of DBs on 1 instance PG (citizen schemas) Lower overhead, simpler management
Data Warehouse Exadata Smart Scan, parallel execution, in-memory ClickHouse (specialized) Hybrid workload (OLTP + DW in one DB)
High-end hardware Exadata engineered system PG (runs on anything) Full-stack HW+SW optimization
Partitioning Range of options (reference, interval, system) PG (basic) 10+ years lead in implementation
Flashback / recovery Flashback Database, Table, Query — any point in time PG (PITR, point-in-time) Faster, more granular recovery
Ecosystem OEM, Data Pump, SQL Developer, Toad, GoldenGate PG (pgAdmin, pg_dump, Patroni) Decades of enterprise tooling

When to use Oracle

  • Critical OLTP systems — banking, payment processing, trading
  • Enterprise consolidation — hundreds of DBs on one RAC cluster (multitenant)
  • Regulated environments — finance, healthcare, government (audit, security, compliance)
  • Oracle ecosystem — E-Business Suite, PeopleSoft, Siebel, JD Edwards
  • Exadata customers — maximum performance for hybrid workload (OLTP + DW)
  • GoldenGate replication — heterogeneous replication (Oracle → Kafka, Oracle → PostgreSQL)
  • Cloud migration — OCI, AWS RDS for Oracle, Azure Oracle Database Service

When to use something else

  • Startup / SME → PostgreSQL (free, sufficient performance, no vendor lock-in)
  • Web / LAMP stack → MySQL (simpler, cheaper, broad support)
  • Cloud-native → Aurora, CockroachDB (architecture for cloud, not port of on-prem to cloud)
  • Need only SQL → PostgreSQL (Oracle overhead not worth it)
  • Horizontal write scaling → Cassandra (RAC scales reads, writes go through one node)

Sources

References, books, and standards: sources/databases/sources.md

Recommended reading

Book Authors ISBN Description
Oracle Database 23ai New Features Oracle Corporation — Official guide to new features — AI Vector Search, JSON Relational Duality, property graphs, schema privileges
Expert Oracle Architecture (3rd ed.) Thomas Kyte, Darl Kuhn 978-1484249602 Comprehensive explanation of Oracle architecture — from storage to RAC and Data Guard

Last revision: 2026-06-03

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