Database Writer Process (DBWn)
Writing Changes to Disk Efficiently 💾
🧠 What Is DBWn?
The Database Writer process (DBWn) is responsible for writing modified (dirty) blocks from the database buffer cache to data files on disk.
Think of DBWn as the delivery truck that takes changes made in memory and persists them safely to disk.
✍️ What DBWn Does
| Function | Description |
|---|---|
| 💽 Writes Dirty Buffers | Moves modified blocks from buffer cache to data files. |
| 🏁 Handles Checkpoints | Coordinates with CKPT to ensure data consistency at checkpoints. |
| 🧷 File Sync & Logging | Syncs file writes and logs Block Written records for recovery. |
| ⚡ Reads Flash Cache | Accesses Flash Cache if configured for faster read/write operations. |
| 📦 Performs Multi-block Writes | Tries to write multiple blocks at once for performance. The size varies by OS. |
🔧 Configuration & Naming
- 🔢 Controlled by
DB_WRITER_PROCESSES(1–100) - 🧠 Oracle auto-tunes based on CPU and processor groups
- 🏷️ Naming convention:
- First 36:
DBW0–DBW9,DBWa–DBWz - Beyond that:
BW36–BW99
- First 36:
💡 DBA Tip of the Day
Too many dirty buffers waiting to be written? Consider tuning DB_WRITER_PROCESSES or using ASMM (Automatic Shared Memory Management) to optimize buffer cache performance.