3, CR, a consistent read (stale) block image 一致读
4, READ, buffer is reserved for a block being read from disk 正在从磁盘上读取块
5, MREC, a block in media recovery mode 处于介质恢复模式
6, IREC, a block in instance (crash) recovery mode处于实例恢复模式
lru_flag
3,'cr', 4,'read',5,'mrec',
6,'irec',7,'write',8,'pi', 9,'memory'
10,'mwrite',11,'donated', 12,'protected',
13,'securefile', 14,'siop',15,'recckpt',
16, 'flashfree', 17, 'flashcur', 18, 'flashna'