11gR2 Clusterware Startup Sequence

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 Daemon

Diskmon

ACFS (ASM Cluster File System) Drivers

Level 2: OHASD oraagent spawns:

MDNSD - Used for DNS lookup

GIPCD - Used for inter-process and inter-node communication

GPNPD - Grid Plug & Play Profile Daemon

EVMD - Event Monitor Daemon

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

This image shows the various levels more clearly:



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