Database Reference
In-Depth Information
When the delta record is created, SQL Server adjusts the delta records statistics on the index page and detects
that there is no space on the page to accommodate the new index value once the delta records are consolidated.
It triggers a page split process, which is done in two atomic steps.
In the first step, SQL Server creates two new leaf-level pages and splits the old page values between them. After
that, it repoints the mapping table to the first newly created page and marks the old page and the delta records for
garbage collection.
Figure
32-12
illustrates this state. At this state, there are no references to the second newly created leaf-level page
from internal pages. The first leaf-level page, however, maintains the link between pages (through the mapping table),
and SQL Server is able to access and scan the second page if needed.
Figure 32-12.
Page splitting: First step
During the second step, SQL Server creates another internal page with key values that represent the new
leaf-level page layout. When the new page is created, SQL Server switches the pointer in the mapping table and marks
the old internal page for garbage collection. Figure
32-13
illustrates this action.
Figure 32-13.
Page splitting: Second step
