GC 2-Way and 3-Way Buffer Cache in Oracle RAC Oracle RAC uses a shared cache architecture where each instance has its own buffer cache. To maintain consistency, Oracle uses the Global Cache Service (GCS) to coordinate access across nodes using mechanisms known as GC 2-Way and GC 3-Way buffer transfers. 🔁 What is Global Cache in RAC? Global Cache ensures block consistency across instances in a RAC cluster. Instead of fetching from disk, Oracle RAC uses Cache Fusion to transfer blocks over the interconnect between nodes, reducing I/O and improving performance. ⚡ GC 2-Way Buffer Transfer A GC 2-Way transfer happens when the block is shipped directly from the current holder to the requesting instance in just two messages. 🔁 Request: Instance A → Instance B 📦 Response: Instance B → Instance A This is fast and efficient because it avoids additional overhead. 📘 Example Instance A runs a DML and needs a block held by Instance B in exclusive mode. B sends it directly...