Latch问题

samyp1234

假设A进程，执行一个SQL命令，需要访问SGA中的数据块，它将持有latch。
那么，此时另一个B进程，需要访问SGA中的另外的不同地址的数据块，这时B能否直接获得latch，还是必须等待A进程释放latch？

非常谢谢大家啊。

chaoping

depends.
If the two address is protected by the same latch, then the second session has to wait until the first session releases the latch.

Some latches are sharable, like CBC latch in oracle 9i+ in some cases;