Data compression page

  • What is the meaning of Data_compression page?

    Data compression is a reduction in the number of bits needed to represent data.
    Compressing data can save storage capacity, speed up file transfer and decrease costs for storage hardware and network bandwidth..

  • For rowstore tables and indexes, use the data compression feature to help reduce the size of the database.
    In addition to saving space, data compression can help improve performance of I/O intensive workloads because the data is stored in fewer pages and queries need to read fewer pages from disk.Oct 27, 2023
  • To compress an index, expand the table that contains the index that you want to compress and then expand the Indexes folder.
    Right-click the table or index to compress, point to Storage and select Manage Compression.
    In the Data Compression Wizard, on the Welcome to the Data Compression Wizard page, select Next.
Page-level compression involves replacing repeating patterns that span multiple column values within a single page of data with shorter symbol strings. As a page fills with data, page compression logic scans the page for repetitive data. From this scan, a page-level compression dictionary is created.

What happens when a table is converted to page compression?

When an existing table that contains data is converted to page compression, each page is rebuilt and evaluated

Rebuilding all the pages causes the rebuilding of the table, index, or partition

Learn how the SQL Server Database Engine implements page compression to help you plan the storage space that you need for your data

What is page compression based on?

It is based on the following two metrics: U: The percentage of update operations on a specific table, index, or partition, relative to total operations on that object

The lower the value of U (that is, the table, index, or partition is infrequently updated), the better candidate it is for page compression

Page compression is implemented through the following three methods:

  1. Row compression: as discussed above
  2. Prefix compression: In each page, for each column, a common value from all rows is identified and stored in a row below the header. After that, from all the rows, that common value is replaced with the reference of header row.
  3. Dictionary compression: Dictionary compression is same concept as that of Prefix compression implemented the second time. ...

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