RAC腦裂(split brain)相關： DTO(disktimeout) - SDTO,LDTO

version : 10.1 - 11.2        
During node join and leave (reconfiguration) in a cluster we need to reconfigure, in that particular case we use Short Disk TimeOut (SDTO) which is in all versions SDTO = MC – reboottime (usually 3 seconds)

來自  CSS Timeout Computation in Oracle Clusterware (文件 ID 294430.1)   

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If a heartbeat failed between the nodes, voting disk write now should complete within SDTO. This is called shortdiskTimeout. There are two disk out parameters used in Oracle Clusterware which are: longdisktimeout (LDTO) and shortdisktimeout (SDTO).
The voting disk write should complete within SDTO when there is a “network heart beat failure”. When there is network heart beat failure, Oracle Clusterware no longer considers the LDTO.  

來自   

以上關於SDTO及LDTO的說法， 可以總結為如下幾句:  

SDTO  -- 節點加入或刪除時cluster需進行reconfiguration的時間，SDTO=MC-rebootime=30-3=27秒 。
            或如果在節點之間的心跳failed，voting disk寫操作應該在SDTO(27秒)時間內完成 。

LDTO  -- 是指正常的RAC操作中允許Votedisk I/O完成超時的時間，為200秒。也就是說， 如果網路心跳failed ,  那麼只會使用到 SDTO ,  
             而不會使用到 LDTO ,  LDTO 這個 200秒 只是在網路心跳正常，進行正常RAC操作時候才會用到 。