oracle的脏块和干净块的块首有SCN的信息吗？求大师解答！

Yong Huang

原帖由 liujiannan047 于 2010-4-2 02:20 发表
原来块首fsc表示事务未提交或者存在块延迟清除，scn直接就记录SCN了。

Actually, fsc (free space credit) is not the same as SCN. They just use the same space as if it was one field (think of this field as a union data structure in C programming). The best description of it is at
http://www.ixora.com.au/q+a/datablock.htm

"SCN or free space credit         6 bytes         If the transaction has been cleaned out, this is the commit SCN or an upper bound thereof. Otherwise the leading two bytes contain the free space credit for the transaction - that is, the number of bytes freed in the block by the transaction."

Yong Huang

cc59

select 是需要构造CR的，因此你不用考虑会读后来你commit的那个scn.