从1gR2起Oracle引入init.ohasd，将其配置在/etc/inittab中，用以启动和管理clusterware相关资源
Pre 11R2
/etc/inittab
h1:2:respawn:/etc/init.evmd run >/dev/null 2>&1 /dev/null 2>&1 /dev/null 2>&1 /dev/null 2>&1 who -r
. run-level 2 Jul 03 07:52 2 0 S
clusterware资源大致可分为4级，其相应启动顺序如下：
先由INIT启动init.ohasd，后者再启动相应的4个进程，然后按顺序依次启动
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
调用crsctl status resource –t可以查看所有component的状态
参考文档ID 1053147.1