Oracle

Oracle Database

Oracle Database is a multi-model database management system. It is the de-facto standard for Fortune 500 mission-critical systems due to its reliability, scalability (RAC), and PL/SQL power.

When to Use

• Mission Critical: Banking, Airlines, Telecoms where 99.999% uptime is required.
• PL/SQL: When you have massive business logic that needs to run close to the data.
• Complex Workloads: OLTP and OLAP in the same DB.

Quick Start

-- Implicit cursor loop in PL/SQL
BEGIN
  FOR r IN (SELECT first_name, last_name FROM employees WHERE department_id = 10)
  LOOP
    DBMS_OUTPUT.PUT_LINE(r.first_name || ' ' || r.last_name);
  END LOOP;
END;
/

Core Concepts

PL/SQL

Procedural Language/SQL. Extremely mature and powerful language stored within the DB.

RAC (Real Application Clusters)

Allows multiple servers to access the same database storage simultaneously. If one server fails, the others keep running (High Availability).

Multi-Tenant (CDB/PDB)

One Container Database (CDB) hosts multiple Pluggable Databases (PDBs). Efficient resource sharing.

Best Practices (2025)

Do:

• Use Oracle 23ai: Leverage "JSON Relational Duality" to view the same data as both Tables and JSON Documents simultaneously.
• Use Tuning Advisor: Oracle's automated tuning tools are excellent.
• Use Flashback: Query data "as of" a timestamp in the past to recover from accidental logical errors.

Don't:

• Don't commit in loops: It kills IO. Commit once at the end.
• Don't treat it like MySQL: Oracle's architecture (Redo, Undo, Shared Pool) is heavier and requires specific tuning.

References

• Oracle Database 23ai Documentation