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What is Extent and types of Extent?It is the basic unit in which space is managed.
- An extent is eight physically contiguous pages. It means that SQL Server database has 16 extents per megabyte.
Extents are classified into two types:
1. Uniform extent
2. Mixed extent
- SQL Server does not allocate whole extents to the tables because to make its space allocation efficient.
1. Uniform extent:
- It is owned by a single object.
- All the eight pages in the extent can only be used by the owning object.
2. Mixed extent:
- It is shared by up to eight objects.
- Each of the eight pages in the extent can be owned by a different object.
- A new table or index is generally allocated pages from mixed extents.
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