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Thread: db & instance

  1. #1
    Join Date
    Apr 2003
    Posts
    17

    Unanswered: db & instance

    I am confused with the term DB & Instance. Is it 2 different terms if yes then how does it differs.

    have a nice day.

  2. #2
    Join Date
    Apr 2003
    Location
    Germany
    Posts
    25
    right,
    the db is the physical database with it's datafiles, logfiles, controlfiles.
    the instance is allocated memory in shared memory with its' defined backendprocesses like pmon, smon, arch, logwr dbwr, chkpt ...
    and the user processes.
    so you do not start a db you start the instance.
    one db could have two instances -> parallel server/Real Application cluster.

    Orca

  3. #3
    Join Date
    Apr 2002
    Location
    California, USA
    Posts
    482

    Smile

    Think about as many people using the same computer in the same time.

    The computer is the database files, the people are the db instances.

    Each instance has its own SGA and processes, attaching to the same set of data (datafiles). Each instance however could have it's own control files.


    Hope that helps,

    clio_usa
    OCP - DBA

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