Partitioning and archiving are two strategies commonly used in SQL Server to improve performance and manage data storage. In this article, we will discuss the concepts of partitioning and archiving, and explore their benefits and considerations.

Partitioning

Partitioning is the process of dividing a large table into smaller, more manageable pieces. There are two main types of partitioning: vertical and horizontal.

Vertical Partitioning

Vertical partitioning involves splitting a table into two or more tables based on columns. This is typically done to improve performance by reducing the number of columns in the main table, which can lead to faster table scans and index operations. It is important to consider which columns to move to the secondary table, as moving columns that are mainly null or take up minimal space may not provide significant benefits.

Within vertical partitioning, there are two strategies: using triggers or implementing a sparse implementation. Triggers can be used to keep the secondary table in sync with the main table, ensuring that any changes made to the main table are reflected in the secondary table. On the other hand, a sparse implementation only adds a row to the secondary table if there is data for one or more columns. This approach reduces space usage and can improve performance by reducing the number of rows to scan.

Vertical partitioning requires manual implementation, as SQL Server does not provide built-in tools for this process. Once the partitioning is done, appropriate indexing can be applied to each table to optimize query performance.

Horizontal Partitioning

Horizontal partitioning involves splitting a table into multiple tables based on rows. This can be done physically or virtually. Physical partitioning allows the tables to be placed on separate filegroups, providing more room for data growth and potentially increasing performance by involving more disks. Virtual partitioning, also known as partitioned views, involves creating separate tables based on partitioning criteria and then using a view to combine them as if they were a single table.

In SQL Server 2005 and later versions, true partitions are available, where a table can be defined as residing on a partition and all sub-tables are managed by SQL Server. This eliminates the need for a view and provides a more seamless experience. However, it requires the table to be empty during the partition creation process.

Horizontal partitioning can improve performance by confining queries to specific partitions based on the partitioning criteria. For example, partitioning a table based on order date can allow queries that include the order date to be limited to a specific partition, resulting in faster query execution. It is important to consider the trade-off of managing multiple tables and ensuring that indexes are added to all partitions when necessary.

Archiving

Archiving is the process of moving data that is no longer actively used by production applications or reports to a separate table or database. This is typically done to free up space and improve performance. Archiving can be done at the table level by creating a job to move old records to an archive table. It becomes more complex when considering foreign key relationships, but it is manageable for larger tables.

Archiving can provide space savings by moving records to a different drive or machine, or by deleting them entirely. It can also improve performance by reducing the total number of rows, which can lead to faster seeks.

Choosing the Right Strategy

When deciding between partitioning and archiving, it is important to have an archiving plan in place for every table, even if the plan is to never archive it. If space is a constraint, moving entire objects may be preferred over partitioning. Partitioning should be considered for performance improvements as a last resort, as it adds complexity and requires careful consideration of the partitioning column.

Before implementing any partitioning or archiving strategy, it is recommended to perform test runs to evaluate the impact on performance and storage. This will help ensure that the chosen strategy aligns with the specific needs of the database.

In conclusion, partitioning and archiving are valuable techniques in SQL Server for improving performance and managing data storage. By understanding the concepts and considerations of each strategy, database administrators can make informed decisions to optimize their SQL Server environments.