The operating system starts ohasd (how):
Once the Operating system starts and finish the boot scrap process it reads /etc/init.d file via the initialisation daemon (INIT daemon >>) called init or init.d. The init tab file is the one it triggers oracle high availability service daemon
INIT daemon is very first daemon to be start at the time of the operating system boot, we can say it is system and service manager for the oracle linuxor any linux flavor. This services are start and stop through script which is stored in the /etc/init.d directory .
OHASD:-
Oracle High Availability Daemon is the introduced in oracle 11g which is manage all clusterware resources , it is responsible to start and monitor all local oracle clusterware daemon. We can say it is anchor for the all the process .
cat /etc/inittab|grep init.ohasd
h1:35:respawn:/etc/init.d/init.ohasd run >/dev/null 2>&1 </dev/null
HAS startup sequence:
– /etc/inittab
– /etc/init.d/init.ohasd
– /etc/rc.d/init.d/ohasd
– $GRID_HOME/bin/ohasd.bin
“/etc/init.d/init.ohasd” is started at runlevel 3 (networked, multi-user mode) or runlevel 5 (runlevel 3 + GUI).Logs present under “$GRID_HOME/log/<host_name>“.
/etc/inittab >>/etc/init.d/init.ohasd>>>/etc/rc.d>init.d/ohasd>>$GRID_HOME/ohasd.bin
“crsctl disable crs” updates a flag in “/etc/orale/scls_scr/<host_name>/root/ohasdstr“.
This file either contains “enable” or “disable” without any carriage return.
If “disable“, “/etc/rc.d/init.d/ohasd” will not startup.
nohup /etc/init.d/init.ohasd run &
ohasd starts agents(whic all agent):
cssdagent - Agent responsible for spawning CSSD. >>> CSSD
orarootagent - Agent responsible for managing all root owned ohasd resources.
CRSD - Primary daemon responsible for managing cluster resources.
CTSSD - Cluster Time Synchronization Services Daemon
Diskmon
ACFS (ASM Cluster File System) Drivers
oraagent - Agent responsible for managing all oracle owned ohasd resources.
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
cssdmonitor - Monitors CSSD and node health (along wth the cssdagent).
CSSDmonitor
to start up daemons (gipcd, mdnsd, gpnpd, ctssd, ocssd,crsd, evmd asm etc), and
crsd starts agents Which)
orarootagent - Agent responsible for managing all root owned crsd resources.
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
oraagent - Agent responsible for managing all oracle owned crsd resources.
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
that start user resources (database, SCAN, listener etc).
http://rafik-dba.blogspot.com/2019/02/oracle-rac-startup-sequence.html
http://oracle-help.com/oracle-rac/rac-11gr2-clusterware-startup-sequence/
