Oracle RAC CSS 超時計算及引數 misscount，Disktimeout 說明 .

http://blog.csdn.net/tianlesoftware/article/details/6728885

一. 概述

在之前的文章：

       RAC 的一些概念性和原理性的知識

       http://blog.csdn.net/tianlesoftware/article/details/5331067      

       提到OCSSD 這個程式是Clusterware最關鍵的程式，如果這個程式出現異常，會導致系統重啟，這個程式提供CSS(Cluster Synchronization Service)服務。 CSS 服務通過多種心跳機制實時監控叢集狀態，提供腦裂保護等基礎叢集服務功能。

       CSS 服務有2種心跳機制： 一種是通過私有網路的Network Heartbeat，另一種是通過Voting Disk的Disk Heartbeat.

       這2種心跳都有最大延時，對於Disk Heartbeat， 這個延時叫作IOT (I/O Timeout);對於Network Heartbeat, 這個延時叫MC(Misscount)。 這2個引數都以秒為單位，預設時IOT大於MC，在預設情況下，這2個引數是Oracle 自動判定的，並且不建議調整。

可以通過如下命令來檢視引數值：

$crsctl get css disktimeout

$crsctl get css misscount

如：

[oracle@rac1 ~]$ crsctl get css disktimeout

200

[oracle@rac1 ~]$ crsctl get css misscount

60

這是這2個引數的預設值。

二. MOS 上相關的幾篇文章

How to start/stop the 10g CRS ClusterWare[ID 309542.1]

10g RAC: Steps To Increase CSS Misscount,Reboottime and Disktimeout [ID 284752.1]

CSS Timeout Computation in OracleClusterware [ID 294430.1]

RAC Assurance Support Team: RAC and OracleClusterware Starter Kit and Best Practices (Generic) [ID 810394.1]

2.1修改CSS Misscount 步驟：

  1)Shut down CRS on all but one node. For exact steps use Note 309542.1

  2)Execute crsctl as root to modify the misscount:

    $ORA_CRS_HOME/bin/crsctl set css misscount

    where is the maximum i/o latency to the voting disk +1 second

  3)Reboot the node where adjustment was made

  4)Start all other nodes shutdown in step 1

With the Patch:4896338 for 10.2.0.1 thereare two additional settings that can be tuned. This change is incorporated into the 10.2.0.2 and 10.1.0.6patchsets.  

These following are only relevant on10.2.0.1 with Patch:4896338，In addition to MissCount, CSS now has two more parameters:

  1)reboottime (default 3 seconds) - the amount of time allowed for a node  to complete a reboot after the CSS daemon hasbeen evicted. (I.E. how  long does ittake for the machine to completely shutdown when you do a reboot)

  2)disktimeout (default 200 seconds) - the maximum amount of time allowed      for a voting file I/O to complete; if thistime is exceeded the voting disk will be marked as offline.  Note that this is also the amount of timethat will be required for initial cluster formation, i.e. when no nodes havepreviously been up and in a cluster.

      $CRS_HOME/bin/crsctl set css reboottime [-force]  ( is seconds)

      $CRS_HOME/bin/crsctl set css disktimeout [-force] (is seconds)

Confirm the new css  misscount setting via ocrdump

2.2 CSS Timeout Computation in OracleClusterware

2.2.1 MISSCOUNTDEFINITION AND DEFAULT VALUES
       The CSS misscount parameterrepresents the maximum time, in seconds, that a network heartbeat can be missedbefore entering into a cluster reconfiguration to evict the node. The followingare the default values for the misscount parameter and their respectiveversions when using Oracle Clusterware* in seconds:

       *CSS misscount default value when using vendor (non-Oracle)clusterware is 600 seconds. This is to allow the vendor clusterwareample time to resolve any possible split brain scenarios.

       On AIX platforms with HACMP starting with 10.2.0.3 BP#1, themisscount is 30. This is documented in Note551658.1

2.2.2 CSS HEARTBEATMECHANISMS AND THEIR INTERRELATIONSHIP
       The synchronization servicescomponent (CSS) of the Oracle Clusterware maintains two heartbeat mechanisms

1.) the disk heartbeat to the voting deviceand

2.) the network heartbeat  across theinterconnect which establish and confirm valid node membership in the cluster.

       Bothof these heartbeat mechanisms have an associated timeout value. The diskheartbeat has an internal i/o timeout interval (DTO Disk TimeOut), in seconds,where an i/o to the voting disk must complete. The misscount parameter (MC), asstated above, is the maximum time, in seconds, that a network heartbeat can be missed. The disk heartbeat i/o timeout interval is directly related tothe misscount parameter setting. There has been some variation in thisrelationship 
between versions as described below:

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9.x.x.x	NOTE, MISSCOUNT WAS A  DIFFERENT ENTITY IN THIS RELEASE
10.1.0.2	No one should be on this version
10.1.0.3	DTO = MC - 15 seconds
10.1.0.4	DTO = MC - 15 seconds
10.1.0.4+Unpublished Bug 3306964	DTO = MC - 3 seconds
10.1.0.4 with CRS II Merge patch	DTO =Disktimeout (Defaults to 200 seconds) Normally OR Misscount seconds only during initial Cluster formation or Slightly before reconfiguration
10.1.0.5	IOT = MC - 3 seconds
10.2.0.1 +Fix for unpublished  Bug 4896338	IOT=Disktimeout (Defaults to 200 seconds) Normally OR Misscount seconds only during initial Cluster formation or Slightly before reconfiguration
10.2.0.2	Same as above (10.2.0.1 with Patch Bug:4896338
10.1 - 11.1	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 â