Reading from a table:
– table scan
– index scan
– keyed read
IAM: list of extents; on read, IAM entries are read and then sorted to generate reads from disk in an optimal way.
Db engine performance is improved on striped sets.
Pages buffer management
The buffer is a set of buffer pages.
Each buffer page has a reference count and a dirty flag.
A buffer management thread periodically scans all pages to detect the ones with a reference count of 0.
If they are dirty, they wil be written to disk and then moved to free pages list.
If not dirty, they will directly moved to the free pages list.