The DBCC command DBCC EXTENTINFO provides information about extents allocations that occur within a database. The command can be used to identify how extents have been allocated and whether the extents being used are mixed or uniform.For every extent allocation, there will be one row in the results. Since extents are comprised of eight pages, there can be as many as eight allocations for an extent when there are single page allocations, such as when mixed extents are used. When uniform extents are used, there will be only one extent allocation and one row returned for the extent.DBCC EXTENTINFO can be extremely useful for investigating how pages are allocated to tables and indexes.Using the DBCC command can be extremely useful when trying to investigate issues related to fragmentation and how pages have been allocated.
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