Fossil/knowledge-base
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

comiiit

Browse Source
This commit is contained in:
Stanislav Hubacek
2026-06-11 15:25:40 +02:00
parent 95d1839f05
commit 3fa11ef0f6
50 changed files with 9336 additions and 33 deletions
Download Patch File Download Diff File Expand all files Collapse all files

207
ORACLE.en.md Normal file
View File

@@ -0,0 +1,207 @@
# 🏛️ 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:
```text
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
```text
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](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*