1. CRSD. This is the primary daemon process and the primary
engine that provides the high-availability features. CRSD man-
ages the application resources; starts, stops, and fails application
resources over; generates events when things happen; and main-
tains configuration profiles in the OCR. If the daemon fails, it
automatically starts.
2. OCSSD. This daemon process presents various nodes participat-
ing in the cluster as members of the cluster, coordinates and inte-
grates with the vendor clusterware if present, and provides group
services. OCSSD enables synchronization between an ASM
instance and the database instances that rely on it for database file
storage. In a RAC setup there has to be a process that ensures the
health of the cluster so a split brain will not occur. If the process
that does the synchronization dies, rebooting the system will be
necessary to ensure that a split brain has not occurred.
Note: A split brain occurs when the nodes in a cluster lose communication
with each other and become confused about which nodes are members of
the cluster and which nodes are not (this occurs when nodes hang or the
interconnects fail).
3. EVMD. This daemon process has the primary function of send-
ing and receiving messages between nodes.
The Oracle CRS stack installed and running under init(1M)
message at the end of the execution indicates that all the relevant infor-
mation required for cluster management was successfully generated and
stored in the OCR file and the CSS voting disk. At this stage, verifying
the size (to ensure it’s not zero) of the two files is also an indication of this
completion.
GSD. The Global Service Daemon (GSD). The GSD process is created
and started as a service. Please note that unlike in Oracle Database 9i,
GSD is treated as a service and is automatically started once the CRS
daemon is started. GSD has no significant role in Oracle Database 10g;
however, it is started so that it can monitor any Oracle 8i or Oracle 9i
databases on the node and to provide backward compatibility.
ONS. Oracle Notification Services (ONS). ONS is configured and
started. ONS is an Oracle service that allows users to send SMS mes-
sages, e-mails, voice notifications, and fax messages in an easily acces-
sible manner. CRS uses the resource application to send notifications
about the state of the database instances to mid-tier applications that
use this information for load-balancing and for fast failure detection.
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