IBM DB2 is a product from IBM, which is a part of the IBM Information Management family. It is a relational database management system (RDBMS) that delivers advanced data management and analytics capabilities for transactional and warehousing workloads.

How IBM DB2 Works: Low-Level Perspective

IBM DB2 architecture can be dissected into a number of key components that work together to process, manage and store data. Let's delve into some of these components for a more granular view of how DB2 works.

1. Database

The topmost level is the database, which is a collection of data, schemas, tables, views, indexes, and other database objects. The database also contains storage spaces and buffer pools which will be elaborated in subsequent sections.

2. Tablespaces

These are storage structures used to hold data and manage storage space allocation. There are different types of tablespaces: System-managed space (SMS), Database-managed space (DMS), and Automatic storage tablespaces (AST).

-- To create a tablespace
CREATE TABLESPACE sample_tbspace MANAGED BY DATABASE 
USING (FILE 'tbspace1' 2000, 
FILE 'tbspace2' 1000);

3. Buffer Pools

Buffer pools are DB2 components that reduce disk I/O and improve the overall performance of DB2. When data is requested, DB2 first checks if the data is available in a buffer pool. If it's there (a 'cache hit'), it will be returned to the user directly, avoiding a disk I/O operation. If it's not there (a 'cache miss'), a disk I/O operation is initiated, and the data is loaded into the buffer pool.

-- To create a buffer pool
CREATE BUFFERPOOL BP1 SIZE 250 PAGESIZE 4 K

4. Locks

Locks are integral to ensuring data integrity and consistency. DB2 uses a variety of locks (like table locks, row locks, etc.) to prevent data conflicts during simultaneous access.

5. Logs

DB2 uses transaction logs to keep track of all data modifications. They help in recovering the database to a consistent state in case of a system failure.

Architecture of IBM DB2

DB2 database is subdivided into logical areas called tablespaces, which house database objects. Database partitioning (DPF) enables data to be split across multiple partitions for parallel processing. The buffer pool serves as an intermediary between the disk storage and application queries.

The Log manager oversees transaction logs, facilitating database recovery in the event of a system failure. The Lock/Latch manager maintains data consistency during concurrent data access.

Rare Gems: Advanced Features and Usage

IBM DB2 is laden with numerous unique features that set it apart and provide value to its users. Let's explore some of these features:

1. BLU Acceleration

BLU Acceleration is a unique feature of DB2 that allows for faster analytics and reporting. It uses technologies like columnar storage, memory optimization, and data skipping to achieve these performance gains.

2. Adaptive Compression

DB2 supports automatic table data compression, which reduces the storage footprint of your data and enhances the overall system performance.

-- To enable adaptive compression on a table
ALTER TABLE sales_data COMPRESS YES ADAPTIVE

3. Time Travel Query

DB2 offers a feature known as Time Travel Query, which allows you to query data as it was at any point in the past, or even as it might be at a point in the future. This is facilitated by the use of temporal tables.

-- Create a temporal table
CREATE TABLE employees
(
empno CHAR(6),
firstnme VARCHAR(12),
hiredate DATE,
...
PERIOD BUSINESS_TIME (start_date, end_date)
)

4. PureXML

DB2's pureXML feature allows XML data to be stored in its hierarchical format within columns of a DB2 table. This allows for better query performance and easier data manipulation using XQuery and SQL/XML.

-- Create a table with an XML column
CREATE TABLE xml_tab (col1 INT, col2 XML)

In conclusion, IBM DB2 is a feature-rich and robust RDBMS offering from IBM, with a deep array of advanced functionalities that can cater to a wide range of data management and analytical needs. The rare gems highlighted above are only a small fraction of DB2's capabilities, and to fully leverage this technology, a thorough understanding and continued exploration of its features is recommended.

Author : Youssef Sbai Idrissi

LinkedIn : https://www.linkedin.com/in/sbaiidrissiyoussef/