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Index Allocation Maps
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indexallocationmaps
Problem
I am a developer reading the book "Querying Microsoft SQL Server 2012." I have come across the following diagram:
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Why are the pages in the first two rows of the diagram (row 1 starting:
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How does the number scheme work e.g. what does
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Directly above the diagram, the book says: "IAM pages for an object are organized as a doubly linked list;" The diagram does not show any links between the pages.
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Why are the pages in the first two rows of the diagram (row 1 starting:
1:174 and row 2 starting: 1:41) not part of an extent? The documentation says: "all pages are stored in extents": -
How does the number scheme work e.g. what does
1:174 mean?-
Directly above the diagram, the book says: "IAM pages for an object are organized as a doubly linked list;" The diagram does not show any links between the pages.
Solution
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They are part of a mixed extent, the diagram just didn't draw a grey box behind them, probably more to keep it from being too busy as much as anything.
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Again, I think this is just meant to simplify and not make the diagram too busy, as well as not give any sort of suggestion that pages will necessarily be linked in a certain order. Surely you can picture the arrows that would represent a doubly-linked list?
For most of this, you're much better off asking the author of the book and creator of the diagram, than a community of peers.
They are part of a mixed extent, the diagram just didn't draw a grey box behind them, probably more to keep it from being too busy as much as anything.
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Data File : Page-
Again, I think this is just meant to simplify and not make the diagram too busy, as well as not give any sort of suggestion that pages will necessarily be linked in a certain order. Surely you can picture the arrows that would represent a doubly-linked list?
For most of this, you're much better off asking the author of the book and creator of the diagram, than a community of peers.
Context
StackExchange Database Administrators Q#129186, answer score: 5
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