Understanding the Difference Between a Table Scan and an Index Scan in DB2

When it comes to database performance optimization in DB2, it is crucial to distinguish between a table scan and an index scan. These two methods of data retrieval play a significant role in query execution efficiency.

Table Scan

A table scan, also known as a full table scan, involves scanning through all rows in a table to identify the required data. This method reads every row sequentially, which can be resource-intensive and time-consuming, especially for large tables. Table scans are generally less efficient and should be avoided if possible.

Index Scan

An index scan, on the other hand, leverages the indexes created on the columns of a table to quickly locate the necessary data. Instead of scanning through all rows, an index scan navigates the index structure to locate the specific rows that satisfy the query criteria. This results in faster data retrieval, improved performance, and reduced resource utilization.

Key Differences

The key difference between a table scan and an index scan lies in their approach to accessing data. While a table scan reads all rows sequentially, an index scan uses index structures to pinpoint the required rows efficiently. Index scans are favored for their speed and optimization benefits, making them a preferred choice for query performance improvement in DB2.

By understanding the distinction between a table scan and an index scan in DB2, database administrators can make informed decisions to enhance query performance and optimize database operations.