11gR2 Clusterware Startup Sequence

11gR2 Clusterware Startup Sequence

The following is the Clusterware startup sequence (image from the "Oracle Clusterware Administration and Deployment Guide):

Don't let this picture scare you too much.  You aren't responsible for managing all of these processes, that is the Clusterware's job!

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:

CRSD - Primary daemon responsible for managing cluster resources.CTSSD - Cluster Time Synchronization Services DaemonDiskmonACFS (ASM Cluster File System) Drivers

Level 2: OHASD oraagent spawns:

MDNSD - Used for DNS lookupGIPCD - Used for inter-process and inter-node communicationGPNPD - Grid Plug & Play Profile DaemonEVMD - Event Monitor DaemonASM - 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 networkSCAN VIP(s) - Single Client Access Name Virtual IPsNode VIPs - One per nodeACFS Registery - For mounting ASM Cluster File SystemGNS VIP (optional) - VIP for GNS

Level 4: CRSD oraagent spawns:

ASM Resouce - ASM Instance(s) resourceDiskgroup - Used for managing/monitoring ASM diskgroups.DB Resource - Used for monitoring and managing the DB and instancesSCAN Listener - Listener for single client access name, listening on SCAN VIPListener - Node listener listening on the Node VIPServices - Used for monitoring and managing servicesONS - Oracle Notification ServiceeONS - Enhanced Oracle Notification ServiceGSD - For 9i backward compatibilityGNS (optional) - Grid Naming Service - Performs name resolution

This image shows the various levels more clearly:

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