Oracle 11g R2 RAC Startup Sesquence

Following is the picture representing RAC startup sequence. Got it from one of the links by Suresh Gandhi's .Thanks a ton for providing this...

http://oracle-info.com/

Without much hassle or discussion with bottom to top approach, I understand now,

OHASD Phase:-

• OHASD (Oracle High Availability Server Daemon) starts Firsts and it will start

OHASD Agent Phase:-

• OHASD Agent starts and in turn this will start

gipcd	Grid interprocess communication daemon, used for monitoring cluster interconnect
mdnsd	Multicast DNS service It resolves DNS requests on behalf of GNS
gns	The Grid Naming Service (GNS), a gateway between DNS and mdnsd, resolves DNS requests
gpnpd	Grid Plug and Play Daemon, Basically a profile similar like OCR contents stored in XML format in $GI_HOME/gpnp/profiles/<peer> etc., this is where used by OCSSD also to read the ASM disk locations to start up with out having ASM to be up, moreover this also provides the plug and play profile where this can be distributed across nodes to cluster
evmd/ evmlogger	Evm service will be provided by evmd daemon, which is a information about events happening in cluster, stop node,start node, start instance etc.

• cssdagent (cluster synchronization service agent), in turn starts

ocssd

Cluster synchronization service daemon which manages node membership in the cluster

If cssd found that ocssd is down, it will reboot the node to protect the data integrity.

• cssdmonitor (cluster synchronization service monitor), replaces oprocd and provides I/O fencing

• OHASD orarootagent starts and in turn starts

crsd.bin	Cluster ready services, which manages high availability of cluster resources , like stopping , starting, failing over etc.
diskmon.bin	disk monitor (diskdaemon monitor) provides I/O fencing for exadata storage
octssd.bin	Cluster synchronization time services , provides Network time protocol services but manages its own rather depending on OS

CRSD Agent Phase:- crsd.bin starts two more agents

crsd orarootagent(Oracle root agent) starts and in turn this will start

gns	Grid interprocess communication daemon, used for monitoring cluster interconnect
gns vip	Multicast DNS service It resolves DNS requests on behalf of GNS
Network	Monitor the additional networks to provide HAIP to cluster interconnects
Scan vip	Monitor the scan vip, if found fail or unreachable failed to other node
Node vip	Monitor the node vip, if found fail or unreachable failed to other node

crsd oraagent(Oracle Agent) starts and in turn it will start (the same functionality in 11gr1 and 10g managed by racgmain and racgimon background process) which is now managed by crs Oracle agent itself.

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ASM & disk groups	Start & monitor local asm instance
ONS	FAN feature, provides notification to interested client
eONS	FAN feature, provides notification to interested client
SCAN Listener	Start & Monitor scan listener
Node Listener	Start & monitor the node listener (rdbms?)