Database Reference
In-Depth Information
Network Switch
Public Network
Interconnect Switch
Cluster
Interconnect
ORADB3
ORADB4
ORADB1
ORADB2
VIP
VIP
SSKY3
VIP
SSKY4
VIP
SSKY1
SSKY2
GIPCD
CRFMOND/LOGD
DISKMON
DISKMON
DISKMON
DISKMON
GPnP
GPnP
GPnP
NM
GM
CSS
CTSS
CTSS
CTSS
CSS
EVM
CSS
EVM
CSS
EVM
EVM
CRS
OCR
CRS
CRS
CRS
HAS
HAS
HAS
HAS
SAN Switch
OLR
OLR
OLR
OLR
prddb
OCR
Vote Disk
AA_00
AB_01
AC_02
AD_03
AE_04
AF_05
AG_06
AH_07
Figure 2-4.
Oracle Clusterware components
Initiated by the Cluster Synchronization Services (CSS) process, the Oracle Cluster Synchronization Service
Daemon or OCSSD is a process that performs the basic synchronization services between the various resources in the
cluster. With the help of the voting disk (created as part of the Oracle Clusterware installation), it arbitrates ownership
of the cluster among cluster nodes in the event of a complete private network failure. OCSSD is a critical daemon
process, and a failure of this process causes the node (server) to reboot.
These services are performed by node membership (NM) service and the group membership (GM) services.
The NM checks the heartbeat across the various nodes in the cluster every second. It also alternates to check
the heartbeat of the disk by performing a read/write operation every second. If the heartbeat/node members do not
respond within 30 seconds, the node (among the surviving nodes) that was started first (master) will start evicting the
other node(s) in the cluster.
NM also checks the voting disk to determine if there is a failure on any other nodes in the cluster. During this
operation, NM will make an entry in the voting disk to inform its vote on availability. Similar operations are performed
by other instances in the cluster. The three voting disks configured also provide a method to determine who in the
cluster should survive. For example, if eviction of one of the nodes is necessitated by an unresponsive action, then the
node that has two voting disks will start evicting the other node.
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