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RAC – 11gR2 startup sequence


 

11gR2 RAC startup

 

Short summary of the startup sequence: INIT spawns init.ohasd (with respawn) which in turn starts the OHASD process (Oracle High Availability Services Daemon).  This daemon spawns 4 processes.

Level 1: OHASD Spawns:

cssdagent         – Agent responsible for spawning CSSD.
orarootagent     – Agent responsible for managing all root owned ohasd resources.
oraagent         – Agent responsible for managing all oracle owned ohasd resources.
cssdmonitor        – Monitors CSSD and node health (along wth the cssdagent).

Level 2: OHASD rootagent spawns:
CSDD (ora.cssd)     – Cluster Synchronization Services
CRSD(ora.crsd)     – Primary daemon responsible for managing cluster resources.
CTSSD(ora.ctssd)     – Cluster Time Synchronization Services Daemon
Diskmon(ora.diskmon)
ACFS (ASM Cluster File System) Drivers

Level 2: OHASD oraagent spawns:

MDNSD(ora.mdnsd)     – Used for DNS lookup
GIPCD(ora.gipcd)     – Used for inter-process and inter-node communication
GPNPD(ora.gpnpd)     – Grid Plug & Play Profile Daemon
EVMD(ora.evmd)     – Event Monitor Daemon
ASM(ora.asm)     – Resource for monitoring ASM instances

Level 3: CRSD spawns:

orarootagent     – Agent responsible for managing all root owned crsd resources.
oraagent         – Agent responsible for managing all oracle owned crsd resources.

Level 4: CRSD rootagent spawns:

Network resource     – To monitor the public network
SCAN VIP(s)     – Single Client Access Name Virtual IPs
Node VIPs         – One per node
ACFS Registery     – For mounting ASM Cluster File System
GNS VIP (optional)     – VIP for GNS

Level 4: CRSD oraagent spawns:

ASM Resouce     – ASM Instance(s) resource
Diskgroup         – Used for managing/monitoring ASM diskgroups.
DB Resource     – Used for monitoring and managing the DB and instances
SCAN Listener     – Listener for single client access name, listening on SCAN VIP
Listener         – Node listener listening on the Node VIP
Services         – Used for monitoring and managing services
ONS         – Oracle Notification Service
eONS         – Enhanced Oracle Notification Service
GSD         – For 9i backward compatibility
GNS (optional)     – Grid Naming Service – Performs name resolution

Taken from MOS Document 1053147.1

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