Oracle 11gR2 Clusterware Startup Sequence

In Oracle 10g RAC and 11gR1 RAC,  Oracle clusterware and ASM are installed in the different Oracle homes, and the Clusterware has to be  up before ASM instance can be started because ASM instance uses the clusterware to access the shared storage.  Oracle 11g R2 introduced the  grid infrastructure home which combines Oracle clusterware and ASM.  The OCR and votingdisk of 11g R2 clusterware can be stored in ASM.  So it seems that ASM needs the clusterware up first to access the shared storage  and the clusterware needs ASM up first before it can access its key data structure: OCR and votingdisk.  So really clusterware and ASM, which one needs to be up first, and which one has to wait for other? This seemed to be the chicken or the egg problem.

Oracle’s solution to this problem is to combines  the clusterware and ASM  into a single Grid Infrastructure home and  comes up a  procedure with  a complex  start up sequence which  mixes  the different components of clusterware and ASM  instance in order.  Oracle Metalink note 11gR2 Clusterware and Grid Home –The full description, the really unreadable diagram and/or any updates to this you can find it in MOS Document 1053147.1.

This description is also from the MOS note stated above

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