The txnID was added to the page header to enable support for incremental backup. As a consequence, it's sufficient to compare a page's txnID to the current txnID to know if it's dirty or not, and spilled pages don't need a cleanup pass to clear their dirty bit on commit so commits of large txns are faster now.
Dropping the explicit P_DIRTY flag in 1.0 is a neat change. What tracks which pages still need to be written back at commit now that the flag is gone?
The txnID was added to the page header to enable support for incremental backup. As a consequence, it's sufficient to compare a page's txnID to the current txnID to know if it's dirty or not, and spilled pages don't need a cleanup pass to clear their dirty bit on commit so commits of large txns are faster now.