Sql-server – How does the transaction log work in SQL Server when i run a DML

Good question. While it is true that view definitions are expanded into the query text very early on in the compilation and optimization process, all sorts of information is tracked with the cached plan that is not directly visible e.g. statistics that were considered 'interesting' for plan exploration, so that we get the expected recompilation if those statistics change. This is true even if the final plan shape chosen did not directly make use of the changed statistics - we should still recompile because there may now be a better plan available.

In a similar vein, a user would reasonably expect that 'using' a view should block any concurrent attempt to change the definition of that view. This should hold true even though the implementation expands view text before any real compilation or optimization occurs. To that end, it makes sense that the view's object_id should be part of the cached plan and an otherwise-very-compatible Intent-Shared lock taken each time that plan is executed. Holding this lock prevents another session acquiring Sch-M (schema modification) on that object and modifying the view while we are logically referencing it (even though it was expanded). Obviously locks on the objects referenced by the view would not be enough.

To the question of whether this sort of thing should be documented or not. The shape of Books Online over the years suggests that documenting something means it has to go through a cycle of deprecation before it can be changed, so unless that apparent policy changes so that 'documentation' is expanded to include 'interesting details that nevertheless might change at any time', it seems unlikely that this sort of internal implementation detail would ever make it into the formal documentation.

No your theory is wrong.

Dirty pages can be written to disc even if the transaction is not yet committed. However it is ensured that they cannot be written before the last transaction log entry that modified the page has been written to disc.

The transaction log records do contain sufficient information both for redo and undo (except for in tempdb where only undo is necessary). If you decide to rollback the transaction then nothing is deleted from the log. Instead compensation log records are written to the log indicating this.