What are the different Types of Pages available?
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GAM and SGAM (Global Allocation Map & Shared GAM):
GAM: Extents have been allocated: 1 – Free space 0 – No space
SGAM: Mixed Extents have been allocated: 1 – Free Space + Mixed Extent and 0 – No space
Each GAM / SGAM covers 64000 extents – 4 GB
PFS (Page Free Space): Percentage of free space available in each page in an extent.
DCM (Differential Changed Map): This tracks the extents that have changed since the last BACKUP DATABASE statement. 1 – Modified, 0 – Not modified
BCM (Bulk Changed Map): This tracks the extents that have been modified by bulk logged operations since the last BACKUP LOG statement. 1 – Modified, 0 – Not modified (Used only in bulk logged Recovery model)
In each data file pages are arranged like below
Along with that we have three different data pages
Data
Index
Text/ Image (LOB, ROW_OVERFLOE, XML)