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Oracle 11g R1/R2 Real Application Clusters Essentials by Syed Jaffer Hussain, Ben Prusinski

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Clusterware startup sequence for Oracle 11g R2

Understanding how the clusterware startup occurs is critical to the diagnosis and resolution of Oracle RAC problems.

In Unix and Linux operating systems, there is a master daemon process named INIT that functions to start up additional system background processes. The INIT process first spawns the init.ohasd process, which in turn starts up the Oracle High Availability Services Daemon (OHASD). In turn, the OHASD daemon then spawns additional Clusterware processes at each startup level as shown next:

  • 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 ...

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