Mark Spiegel <[EMAIL PROTECTED]> wrote: > > I take this to mean that paged-aligned sector I/O will always be used > for all the DB types. Will there ever be an I/O to a DB file that will > not follow these rules.
When first opening a database, 100 bytes are ready from the very beginning of the database file. Part of this header tells us how big the pages are. The initial read is page-aligned but it is not a read of a complete page, obviously, since at that time we do not know how big the page is. Otherwise, I think all database I/O is of complete pages. There might be an exception for updating the change counter in the header. I'd have to check. > What about the journal types? Will their I/O > be sector sized and aligned I/O as well? No. Journals are mostly sequentially written, increasing the file size as it is written. There is a sector-sized header at the beginning of the journal that is skipped at first and then overwritten at the end. If the cache spills, this sector-sized header might also be repeated at various points in the middle of the file. -- D. Richard Hipp <[EMAIL PROTECTED]> ----------------------------------------------------------------------------- To unsubscribe, send email to [EMAIL PROTECTED] -----------------------------------------------------------------------------
