208 lines
11 KiB
Markdown
208 lines
11 KiB
Markdown
# 🏛️ Oracle Database
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## Overview
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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.
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## Architecture
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### Oracle instance + database
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```
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Oracle Instance (memory + processes)
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├── System Global Area (SGA)
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│ ├── Database Buffer Cache
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│ ├── Shared Pool (library cache, dictionary cache)
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│ ├── Redo Log Buffer
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│ ├── Java Pool
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│ ├── Large Pool (backup, parallel)
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│ └── In-Memory Column Store (option)
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├── Program Global Area (PGA) — per session
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└── Background processes
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├── PMON (process monitor)
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├── SMON (system monitor)
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├── DBWn (database writer)
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├── LGWR (log writer)
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├── CKPT (checkpoint)
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├── ARCn (archiver)
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└── MMON (manageability monitor)
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```
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### Multitenant architecture (12c+)
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```
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Container Database (CDB)
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├── Root (CDB$ROOT) — metadata, system objects
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├── Seed (PDB$SEED) — template for new PDBs
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├── Pluggable Database 1 (PDB1) — application A
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├── Pluggable Database 2 (PDB2) — application B
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└── Pluggable Database 3 (PDB3) — application C
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```
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Each PDB looks like a separate database but shares SGA and background processes. Advantage: higher density, simpler patching (CDB level), resource management per PDB.
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### Oracle RAC (Real Application Clusters)
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Multi-instance architecture — multiple servers access the same storage:
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```text
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Node 1 ─── Oracle ASM ─── Shared Storage (SAN/NFS)
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Node 2 ─── Oracle ASM ─── Shared Storage (SAN/NFS)
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Node 3 ─── Oracle ASM ─── Shared Storage (SAN/NFS)
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│
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Cache Fusion (private interconnect)
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```
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- Up to 64 nodes in a cluster
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- **Cache Fusion** — transfer of dirty blocks between instances via private interconnect (RAC-specific)
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- **ASM** (Automatic Storage Management) — clustered filesystem + volume manager
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- **Service** — workload routing (primary, report, batch)
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### Oracle Data Guard
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| Mode | Protection | Latency | Use case |
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|------|-----------|---------|----------|
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| **Maximum Protection** | Zero data loss (sync) | Highest | Critical systems |
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| **Maximum Availability** | Zero data loss (sync, fallback to async) | High | Enterprise standard |
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| **Maximum Performance** | Async | Lowest | Remote DR |
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- **Active Data Guard** — standby for reads (reporting, backup) — requires license
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- **Far Sync** — synchronous write to remote standby via async (compromise)
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### Oracle Exadata
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Hardware+software platform for Oracle DB:
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| Component | Description |
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|-----------|-------------|
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| **Database Servers** | x86 (Xeon), 2-8× per rack, NVMe, 1.5-6 TB RAM |
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| **Storage Servers** | Total capacity up to 2.7 PB raw per rack |
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| **Smart Scan** | Predicate filtering at the storage layer (instead of DB server) |
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| **Smart Flash Cache** | Multiple caching layers (RAM, Flash, disk) |
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| **RDMA over Converged Ethernet** | Low latency between DB and storage servers |
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Suitable for: largest OLTP, data warehousing, consolidation.
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## Key enterprise features
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| Feature | Description | Competition |
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|---------|-------------|-------------|
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| **RAC** | Shared-everything cluster up to 64 nodes | MSSQL AlwaysOn FCI (2 nodes) |
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| **Active Data Guard** | Standby for reads, far sync, automatic failover | MSSQL AlwaysOn AG, PostgreSQL streaming |
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| **Partitioning** | Range, List, Hash, Composite, interval, reference | PostgreSQL (declarative partitioning 10+) |
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| **Advanced Compression** | Columnar, HCC (Exadata), OLTP compression | InnoDB page compression, PG TOAST |
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| **In-Memory** | Column store in SGA for real-time analytics | PG (no native), MSSQL (columnstore index) |
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| **Advanced Security** | TDE, data redaction, VPD, audit vault, database firewall | PG (pgcrypto, pgaudit), MSSQL (TDE, Always Encrypted) |
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| **Flashback** | Querying historical data (Flashback Query, Table, Database) | PG (temporal tables via extension), MSSQL (system-versioned) |
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| **Sharding** | System-managed, composite, user-defined | MongoDB (native), Vitess (MySQL), Citus (PG) |
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| **ASM** | Clustered filesystem + volume manager | VMware VMFS, Windows CSV |
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## Oracle licensing detail
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### Editions
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| Edition | Metric | Price (indicative) | Limitations |
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|---------|--------|-------------------|-------------|
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| **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 |
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| **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** |
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| **Oracle Database Enterprise Edition (RAC)** | Per core (EE + RAC option) | ~$47,500 + $23,000/core | EE + RAC clustering |
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### Optional licenses (options) — EE only
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| Option | Price (indicative / core) | Use case |
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|--------|--------------------------|----------|
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| **Real Application Clusters (RAC)** | ~$23,000 | Multi-instance cluster |
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| **Active Data Guard** | ~$10,000 | Standby for reads, far sync, automatic failover |
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| **Partitioning** | ~$11,500 | Range, list, hash, interval, reference, system |
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| **Advanced Compression** | ~$11,500 | OLTP compression, HCC (Exadata), JSON compression |
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| **Advanced Security** | ~$15,000 | TDE, data redaction, database firewall |
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| **In-Memory Database** | ~$23,000 | Column store in SGA for real-time analytics |
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| **Database Vault** | ~$5,750 | Separation of duties, multi-tenancy security |
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| **Multitenant (EE)** | Free (since 21c) | CDB/PDB — max 3 PDB per CDB in EE without license. Unlimited with Multitenant option (~$17,500) |
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| **Spatial / Graph** | ~$5,750 | Geospatial data, property graph |
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| **Label Security** | ~$5,750 | Row-level security with classifications |
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### Oracle Cloud (OCI) licensing
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| Service | Model | Price | Note |
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|---------|-------|-------|------|
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| **OCI Base Database (RDS-like)** | BYOL or License Included | ~$1-5/hour (BYOL cheaper) | Single instance or RAC, automatic backup, patching |
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| **OCI Exadata Database Service** | BYOL or License Included | ~$5-30/hour (depending on shape) | Exadata X9M/X10M in OCI, elastic, full Exadata features |
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| **OCI Autonomous Database** | Per CPU (ECPU) | ~$0.50-3.00/ECPU/hour | Auto-tuning, auto-scaling, auto-patching |
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| **BYOL (Bring Your Own License)** | Own Oracle license in OCI | Infrastructure only | Can use existing perpetual license, including support |
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### RAC sizing — license cost
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```text
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4-node RAC, each node 2× EPYC 9654 (96C) = 192 cores per node
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Core factor 0.5 → 96 Oracle licenses per node
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4 × 96 = 384 Oracle EE licenses
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EE: 384 × $47,500 = $18,240,000
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RAC option: 384 × $23,000 = $8,832,000
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Support 22% annually: ($18,240,000 + $8,832,000) × 0.22 = $5,955,840/year
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Tip: For RAC, consider smaller CPUs (e.g., 64C instead of 96C) — license cost often exceeds hardware cost.
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```
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### Oracle vs PostgreSQL — comparison
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| Area | Oracle | PostgreSQL |
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|------|--------|------------|
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| **License** | Proprietary (per core, ~$17.5k-47.5k/core + 22% support annually) | Open source (PostgreSQL license, MIT-like) |
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| **RAC clustering** | Native, shared-everything | None (Citus = shared-nothing) |
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| **Multitenant** | CDB/PDB architecture | None (schemas per tenant) |
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| **Parallel execution** | Mature (auto DOP, parallel index scan) | Good (parallel seq/index scan, join) |
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| **Storage management** | ASM (integrated) | OS volume / LVM |
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| **Materialized views** | With refresh on commit, query rewrite | No query rewrite |
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| **Partitioning** | 40+ options (interval, referential, system) | Declarative (range, list, hash since 10+) |
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| **In-memory** | Columnar in SGA | Not native |
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| **Standby usage** | Active Data Guard (read-only, license) | Hot standby (read-only, free) |
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| **Cloud** | OCI (Oracle Cloud), AWS RDS, Azure | All clouds (native) |
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## Recommendations — where Oracle is better
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| Area | Oracle | Competition | Why Oracle |
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|------|--------|-------------|------------|
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| **License cost (4-node RAC, 384 cores)** | ~$50M (1st year incl. support) | PostgreSQL: $0 | Oracle: 22% support annually on license fee |
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| **Vendor lock-in** | High (GoldenGate migration difficult, PL/SQL specific) | PostgreSQL: none | MySQL and PG have migration tools from Oracle (ora2pg, AWS DMS) |
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| **Enterprise OLTP** | RAC + ASM, zero-downtime patching | MSSQL (FCI limit 2 nodes) | Shared-everything cluster, transparent failover |
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| **Finance / Banking** | Audit Vault, Database Vault, TDE, VPD | PG (pgaudit, row-level security) | Compliance certifications (SOX, PCI, GDPR) |
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| **Consolidation** | Multitenant (CDB/PDB) — hundreds of DBs on 1 instance | PG (citizen schemas) | Lower overhead, simpler management |
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| **Data Warehouse** | Exadata Smart Scan, parallel execution, in-memory | ClickHouse (specialized) | Hybrid workload (OLTP + DW in one DB) |
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| **High-end hardware** | Exadata engineered system | PG (runs on anything) | Full-stack HW+SW optimization |
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| **Partitioning** | Range of options (reference, interval, system) | PG (basic) | 10+ years lead in implementation |
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| **Flashback / recovery** | Flashback Database, Table, Query — any point in time | PG (PITR, point-in-time) | Faster, more granular recovery |
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| **Ecosystem** | OEM, Data Pump, SQL Developer, Toad, GoldenGate | PG (pgAdmin, pg_dump, Patroni) | Decades of enterprise tooling |
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### When to use Oracle
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- **Critical OLTP systems** — banking, payment processing, trading
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- **Enterprise consolidation** — hundreds of DBs on one RAC cluster (multitenant)
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- **Regulated environments** — finance, healthcare, government (audit, security, compliance)
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- **Oracle ecosystem** — E-Business Suite, PeopleSoft, Siebel, JD Edwards
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- **Exadata customers** — maximum performance for hybrid workload (OLTP + DW)
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- **GoldenGate replication** — heterogeneous replication (Oracle → Kafka, Oracle → PostgreSQL)
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- **Cloud migration** — OCI, AWS RDS for Oracle, Azure Oracle Database Service
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### When to use something else
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- **Startup / SME** → PostgreSQL (free, sufficient performance, no vendor lock-in)
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- **Web / LAMP stack** → MySQL (simpler, cheaper, broad support)
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- **Cloud-native** → Aurora, CockroachDB (architecture for cloud, not port of on-prem to cloud)
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- **Need only SQL** → PostgreSQL (Oracle overhead not worth it)
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- **Horizontal write scaling** → Cassandra (RAC scales reads, writes go through one node)
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## Sources
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References, books, and standards: [sources/databases/sources.en.md](sources/databases/sources.en.md)
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### Recommended reading
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| Book | Authors | ISBN | Description |
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|------|---------|------|-------------|
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| Oracle Database 23ai New Features | Oracle Corporation | — | Official guide to new features — AI Vector Search, JSON Relational Duality, property graphs, schema privileges |
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| Expert Oracle Architecture (3rd ed.) | Thomas Kyte, Darl Kuhn | 978-1484249602 | Comprehensive explanation of Oracle architecture — from storage to RAC and Data Guard |
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*Last revision: 2026-06-03*
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