global resource dicrectory 的内容:
1,data block address
2,读入群集节点buffer caches最新版本data block的位置.
3,节点实例持有数据块锁定模式:n or shared or exclusive
4,节点实例持有数据块的角色:local or global
On most platforms, Oracle uses the Lamport SCN generation scheme when the
value for MAX_COMMIT_PROPAGATION_DELAY is larger than a platform-specific
threshold. This is generally the default and this value is typically set to 7 seconds