Tuesday, May 20, 2008


The synchronization services component (CSS) of the Oracle Clusterware maintains two heartbeat mechanisms
1.) the disk heartbeat to the voting device and
2.) the network heartbeat  across the interconnect--which establish and confirm valid node membership in the cluster.
Both of these heartbeat mechanisms have an associated timeout value.
The disk heartbeat has an internal i/o timeout interval (IOT), in seconds,
where an i/o to the voting disk must complete.
The misscount parameter (MC), as stated above, is the maximum time, in seconds, that a network heartbeat  can be missed.
The disk heartbeat i/o timeout interval is directly related to the misscount parameter setting.


If I/O latencies to the voting disk are greater than the default IOT calculations , the cluster may experience CSS node evictions depending on

(a)the Oracle Clusterware (CRS) version,

(b)whether merge patch has been applied and

(c)the state of the Cluster.

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