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Saturday, June 23, 2018

Steps To modify CSS Misscount, Reboottime and Disktimeout

Set parameters to avoid node eviction in RAC environment :- 

Node eviction is quite sometimes happening in Oracle RAC environment on any platform and troubleshooting and finding root cause for node eviction is very important for DBAs to avoid same in the future.

To avoid node eviction,adjust some parameters of CSS (cluster synchronization service) as per our network connectivity.

MissCount: (default 30 seconds)The MissCount is the maximum time, in seconds, that a cluster heartbeat (messages sent between nodes over the network interconnect or through voting disk; the prime indicator of connectivity), can be missed before entering into a cluster reconfiguration to evict the node.

RebootTime:(default 3 seconds) -the amount of time allowed for a node to complete a reboot after the CSS daemon has been evicted.

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

MISSCOUNT DEFINITION AND DEFAULT VALUES

The CSS misscount parameter represents the maximum time, in seconds, that a network heartbeat can be missed before entering into a cluster reconfiguration to evict the node.

The following are the default values for the misscount parameter and their respective versions when using Oracle Clusterware* in seconds:

* By default Misscount is less than Disktimeout seconds

From 11gR2, these settings can be changed online without taking any node down:

Execute crsctl as root to get the values:

[oracle@rac2 ~]$ crsctl get css misscount
CRS-4678: Successful get misscount 60 for Cluster Synchronization Services.

[oracle@rac2 ~]$ crsctl get css reboottime
CRS-4678: Successful get reboottime 3 for Cluster Synchronization Services.

[oracle@rac2 ~]$ crsctl get css disktimeout
CRS-4678: Successful get disktimeout 200 for Cluster Synchronization Services.

Execute crsctl as root to modify the misscount:

$CRS_HOME/bin/crsctl set css misscount n

$CRS_HOME/bin/crsctl set css reboottime n

$CRS_HOME/bin/crsctl set css disktimeout n



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