It is not safe to infer the status bits from the B-tree page
level, because after MLOG_COMP_LIST_END_COPY_CREATED, the
level will not be initialized before the records have been inserted.
(Bug #7973)

  Implement more compact InnoDB record format.
  Old format is available as CREATE TABLE ... ROW_FORMAT=DYNAMIC.

  Merge InnoDB-4.0.5: new isolation levels READ COMMITTED and READ UNCOMMITTED now supported, selective deadlock resolution
mysqld.cc:
  Change MySQL default isolation level to REPEATABLE READ; note that InnoDB has always had that default, and BDB and MyISAM always run at SERIALIZABLE level anyway