What is page compression in SQL Server?
Page-level compression compresses data by storing repeating values and common prefixes only once and then making references to those values from other locations within the table. When page compression is applied to a table, row compression techniques are also applied.
Are databases compressed?
Databases avoid lossy compression at the backend. However, applications might accept a lower quality using lossy techniques, especially for images, audio, videos. Among lossless techniques, all compressed data is stored in binary. Run-Length Encoding is the simplest.
How do I enable page compression?
On the Select Compression Type page, select the compression type to apply to each partition in the table or index you want to compress. When finished, select Next. Select to configure the same compression setting for all partitions. This enables the selection box and disables the Compression Type column in the grid.
When to use page compression in SQL Server?
Clearly, PAGE compression is the best option for index ids 1 and 3. Index id 2 does not seem to benefit so much. Referring to the earlier results, you can see that indexes 1 and 3 are the primary key and a non-clustered index.
How to know if a table is compressed in a database?
Find out if any of your tables are compressed in your database using the query below. Compressed tables can save space and make queries run faster.
How to compress an index in SQL Server?
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, click Next.
How to see if data pages are page-compressed?
To see whether or not data pages are indeed currently “PAGE” compressed, you can use the undocumented DMF sys.dm_db_database_page_allocations (). The is_page_compressed field contains the info you are looking for. You will need to use the DETAILED mode (i.e. 5th parameter) or else the values in that field will all be NULL.