# Layers and Components > [!Note] > `SQL Server is organized in modular layers that handle client communication, query processing, storage management, in-memory OLTP, OS abstraction, and utilities.` 1. **Protocol Layer** - Manages external application communication using TDS (Tabular Data Stream) over TCP/IP. - Translates network messages into internal requests for the database engine. 2. **Query Processor** - **Parsing & Compilation:** Parses T-SQL, validates syntax, and generates an initial query tree. - **Query Optimization:** Uses statistics and costing to produce an efficient execution plan. - **Query Execution:** Orchestrates plan execution, handling parallelism and memory grants. 3. **Storage Engine** - Handles physical data access on disk. - Manages transactions, logging (transaction log), locking, and concurrency control. 4. **In-Memory OLTP Engine** - Specialized engine for memory-optimized tables and natively compiled stored procedures to reduce latency and blocking. 5. **SQLOS/PAL** - Abstracts operating system services for scheduling, memory and resource management, and deadlock detection across platforms. 6. **Utilities** - Maintenance and administrative tools such as DBCC commands, backup/restore operations, and bulk copy (BCP). ![[Pasted image 20250527111213.png]] --- ## ## References - Korotkevitch, D. (2022). _SQL Server advanced troubleshooting and performance tuning: Best practices and techniques_. O’Reilly Media. - Nevarez, B. (2022). _SQL Server query tuning and optimization: Optimize Microsoft SQL Server 2022 queries and applications_. Packt Publishing.