Oracle Database

A Model Context Protocol (MCP) server that enables GitHub Copilot and other LLMs to execute read-only SQL queries against Oracle databases.

npm version License: AGPL v3 mcp-oracle-database MCP server

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⚠️ Breaking Changes in v2.0

DATE, TIMESTAMP, TIMESTAMP WITH TIME ZONE, and TIMESTAMP WITH LOCAL TIME ZONE columns are now returned as formatted strings (YYYY-MM-DD HH:mm:ss) instead of raw JavaScript Date objects.

The timezone is controlled by ORACLE_TIMEZONE (IANA name). If unset it falls back to the server's system timezone, which may differ across machines.

Action required — add ORACLE_TIMEZONE to your .env or MCP env block:

ORACLE_TIMEZONE=UTC        # or e.g. America/Chicago

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Table of Contents

1. Installation
2. Configure VS Code
3. Optional: Create a Read-Only User
4. Features
5. Available Tools
6. Configuration Reference
7. Development
8. Security Considerations
9. Troubleshooting
10. Documentation
11. Licensing

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📦 Installation

From npm (quickest)

npm install -g mcp-oracle-database

Build from Source

git clone https://github.com/tannerpace/mcp-oracle-database.git
cd mcp-oracle-database
npm install
npm run build

macOS Apple Silicon (M1/M2/M3/M4) with no Oracle yet? See the macOS Setup Guide to spin up Oracle XE 21c locally via Colima.

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🔌 Configure VS Code

Create .vscode/mcp.json in your workspace (or add to your global MCP config).

Option A — From Source

{
  "servers": {
    "oracleDatabase": {
      "type": "stdio",
      "command": "node",
      "args": ["/absolute/path/to/mcp-oracle-database/dist/server.js"],
      "env": {
        "ORACLE_CONNECTION_STRING": "localhost:1521/XE",
        "ORACLE_USER": "system",
        "ORACLE_PASSWORD": "OraclePwd123",
        "ORACLE_TIMEZONE": "UTC",
        "ORACLE_POOL_MIN": "2",
        "ORACLE_POOL_MAX": "10",
        "QUERY_TIMEOUT_MS": "30000",
        "MAX_ROWS_PER_QUERY": "1000",
        "ENFORCE_READ_ONLY_QUERIES": "true",
        "MCP_MAX_RESPONSE_CHARS": "50000",
        "MCP_MAX_ROWS_IN_RESPONSE": "200",
        "MCP_MAX_STRING_LENGTH": "500"
      }
    }
  }
}

Replace /absolute/path/to/mcp-oracle-database with the real path on your machine (e.g. /Users/yourname/GITHUB/mcp-oracle-database).

Option B — From npm Global Install

{
  "servers": {
    "oracleDatabase": {
      "type": "stdio",
      "command": "mcp-database-server",
      "env": {
        "ORACLE_CONNECTION_STRING": "localhost:1521/XE",
        "ORACLE_USER": "your_user",
        "ORACLE_PASSWORD": "your_password",
        "ORACLE_TIMEZONE": "UTC",
        "ORACLE_POOL_MIN": "2",
        "ORACLE_POOL_MAX": "10",
        "QUERY_TIMEOUT_MS": "30000",
        "MAX_ROWS_PER_QUERY": "1000",
        "ENFORCE_READ_ONLY_QUERIES": "true",
        "MCP_MAX_RESPONSE_CHARS": "50000",
        "MCP_MAX_ROWS_IN_RESPONSE": "200",
        "MCP_MAX_STRING_LENGTH": "500"
      }
    }
  }
}

After saving, reload VS Code and open a Copilot chat in Agent mode. Try:

"What tables are in the database?"
"Describe the HELP table"
"Show me 5 rows from the HELP table"

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Optional: Create a Read-Only User

Using SYSTEM is fine for local testing. For any real database, use a dedicated read-only user:

-- Connect: sqlplus system/OraclePwd123@localhost:1521/XEPDB1

CREATE USER readonly_user IDENTIFIED BY secure_password;
GRANT CREATE SESSION TO readonly_user;
GRANT SELECT ANY TABLE TO readonly_user;

-- Or restrict to specific tables:
-- GRANT SELECT ON myschema.orders TO readonly_user;
-- GRANT SELECT ON myschema.customers TO readonly_user;

Then update your .env or MCP config:

ORACLE_CONNECTION_STRING=localhost:1521/XEPDB1
ORACLE_USER=readonly_user
ORACLE_PASSWORD=secure_password

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Features

• 🔒 Read-only access — Dedicated read-only database user for security
• 📡 stdio transport — No HTTP server; communicates via standard input/output
• ⚡ Connection pooling — Efficient Oracle connection management
• 📊 Schema introspection — Query table and column information
• 🔍 Advanced schema discovery — 5 specialized tools for tables, relationships, and data patterns
• 💾 In-memory caching — LRU cache with 5-minute TTL for fast repeated access
• 📝 Audit logging — All queries logged with execution metrics
• ⏱️ Timeout protection — Prevents long-running queries
• 🛡️ Result limits — Configurable row limits to prevent memory issues
• 🍎 No Oracle Client needed — Uses node-oracledb Thin Mode (pure JS, works on Apple Silicon)

Architecture

GitHub Copilot / LLM
        ↓ (MCP Protocol)
  MCP Client (spawns process)
        ↓ (JSON-RPC over stdio)
    MCP Server (Node.js)
        ↓ (node-oracledb Thin Mode)
  Oracle Database (read-only user)

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Available Tools

Core Tools

query_database

Execute read-only SQL SELECT queries.

{
  "query": "SELECT table_name FROM user_tables FETCH FIRST 10 ROWS ONLY",
  "maxRows": 10
}

get_database_schema

Get a table list or column details for a specific table.

{ "tableName": "ORDERS" }

Schema Discovery Tools

Tool	Purpose	Cached
listTables	All accessible tables with metadata & optional row counts	✅
describeTable	Column types, constraints, primary/foreign keys	✅
getTableRelations	Foreign key relationships in JSON	✅
getSampleValues	Sample values to understand data formats	❌
suggestRelatedTables	Find related tables by FK, naming, shared columns	❌

📖 See Schema Discovery Documentation for full details and examples.

Example Copilot Prompts

"List all tables in the database"
"Describe the ORDERS table and its relationships"
"How many active users are there?"
"What are the top 5 products by sales this month?"
"Show me recent transactions for customer ID 12345"

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Configuration Reference

All settings can go in .env or as env keys in your VS Code MCP config.

# Oracle Database Connection
ORACLE_CONNECTION_STRING=localhost:1521/XE    # host:port/service
ORACLE_USER=system
ORACLE_PASSWORD=OraclePwd123

# Timezone (REQUIRED for consistent date/timestamp output)
ORACLE_TIMEZONE=UTC                          # IANA timezone, e.g. America/New_York

# Connection Pool
ORACLE_POOL_MIN=2
ORACLE_POOL_MAX=10

# Query Safety
QUERY_TIMEOUT_MS=30000           # max query time in ms
MAX_ROWS_PER_QUERY=1000          # max rows Oracle will fetch
MAX_QUERY_LENGTH=50000           # max SQL length in chars
ENFORCE_READ_ONLY_QUERIES=true   # reject non-SELECT statements

# MCP Response Limits
MCP_MAX_RESPONSE_CHARS=50000     # hard cap on total response size
MCP_MAX_ROWS_IN_RESPONSE=200     # max rows per tool call response
MCP_MAX_STRING_LENGTH=500        # max chars per string field

# Logging
LOG_LEVEL=info
ENABLE_AUDIT_LOGGING=true
ENABLE_FILE_LOGGING=true
LOG_DIR=./logs
NODE_ENV=development

Large schemas: If your database has 500+ tables, raise MCP_MAX_RESPONSE_CHARS to 100000.

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Development

Scripts

npm run build          # Compile TypeScript → dist/
npm run dev            # Watch mode compilation
npm run clean          # Remove dist/
npm run typecheck      # Type-check without compiling
npm start              # Start MCP server (requires build first)
npm run test-client    # Core tool tests against live Oracle DB
npm run test-discovery # Schema discovery tool tests

Project Structure

mcp-oracle-database/
├── src/
│   ├── server.ts               # MCP server entry point
│   ├── client.ts               # Core test client
│   ├── test-discovery.ts       # Discovery tools test client
│   ├── config.ts               # Zod-validated configuration
│   ├── database/
│   │   ├── oracleConnection.ts # Connection pool manager
│   │   ├── queryExecutor.ts    # Query execution + safety checks
│   │   └── types.ts
│   ├── tools/
│   │   ├── queryDatabase.ts    # query_database tool
│   │   ├── getSchema.ts        # get_database_schema tool
│   │   └── discovery/          # 5 schema discovery tools + cache
│   └── utils/
│       ├── logger.ts           # Lightweight file + console logger
│       └── responseFormatter.ts # MCP response size management
├── dist/                       # Compiled output (git-ignored)
├── .env                        # Your credentials (git-ignored)
├── .env.example                # Template
└── package.json

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Security Considerations

1. Read-Only User — Database user should have only SELECT privileges in production
2. SQL Safety — The server trusts the LLM to generate valid SQL; the read-only user is the safety net
3. Query Limits — Row count and timeout limits prevent resource exhaustion
4. Audit Logging — All queries logged with timestamps for review
5. Local First — Designed to run on your machine; can still connect to remote databases

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Troubleshooting

Connection failed

Error: ORA-12545: Connect failed because target host or object does not exist

• Is Oracle running? docker ps | grep oracle-xe
• Check the port: docker ps should show 0.0.0.0:1521->1521/tcp
• Try localhost:1521/XE for SYSTEM, localhost:1521/XEPDB1 for other users

Wrong service name

Service	Use for
localhost:1521/XE	SYSTEM user, DBA operations
localhost:1521/XEPDB1	Regular application users

Permission denied

Error: ORA-00942: table or view does not exist

GRANT SELECT ANY TABLE TO your_user;

Response too large

Response for tool 'listTables' exceeded MCP_MAX_RESPONSE_CHARS

MCP_MAX_RESPONSE_CHARS=100000

Colima / Docker issues (macOS)

See macOS Setup Guide — Troubleshooting.

Thin Mode note

This project uses node-oracledb Thin Mode — a pure JavaScript driver that requires no Oracle Instant Client. It works on all platforms including Apple Silicon Macs.

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Documentation

📚 Guides:

• macOS Setup Guide — Local Oracle XE setup on Apple Silicon
• Schema Discovery Guide — Advanced schema introspection tools
• Schema Discovery Quick Reference — Cheat sheet for all discovery tools
• Schema Discovery Examples — MCP message examples
• VS Code Integration Guide — Set up with GitHub Copilot
• Claude Desktop Integration Guide — Set up with Claude Desktop
• MCP Integration Guide — MCP protocol deep dive
• Architecture Overview — System architecture diagram
• Logging Configuration — Logging setup and configuration

📝 Custom Instructions:

• .github/copilot-instructions.md — Project-wide Copilot instructions
• .github/instructions/ — Language-specific coding guidelines

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Licensing

This project is licensed under the GNU Affero General Public License v3.0 (AGPL-3.0).

You are free to use, modify, and distribute this software under the terms of the AGPL-3.0. Any modified version deployed as a network service must make its source code available to users of that service.

See LICENSE.md for the full license text.

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Oracle is a registered trademark of Oracle Corporation. This project is not affiliated with, endorsed by, or sponsored by Oracle Corporation.