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  1. #1
    Join Date
    Mar 2004
    Posts
    33

    Arrow Unanswered: NODE vs INSTANCE

    Hi all,

    I have always been confusing about the definition of
    Node and Instance in DB2.

    Does a node means a physical server that host a DB2?
    Does an instance refers to an instance hosted within a node?

    Could all you guys help?

    MUCH THANKS
    ME

  2. #2
    Join Date
    Jun 2003
    Location
    Toronto, Canada
    Posts
    5,516
    Provided Answers: 1
    It's all in the manuals.

    database manager instance
    (1) A logical database manager environment similar to an image of the actual database manager environment. It is possible have several instances of the database manager product on the same workstation. Use these instances to separate the development environment from the production environment, tune the database manager to a particular environment and protect sensitive information.
    (2) The DB2 code that manages data. An instance has its own databases (which other instances cannot access), and all its database partitions share the same system directories. It also has separate security from other instances on the same computer.

    ...

    database node
    See database partition.

    ...

    database partition
    In a partitioned database environment, a part of the database that consists of its own user data, indexes, configuration files, and transaction logs.

  3. #3
    Join Date
    Aug 2003
    Posts
    106
    Whenever a local database is created the following directory structure is created:

    1.0 directory path
    1.1 instance name
    1.1.1 nodexxxx
    1.1.1.1 database directory 1
    1.1.1.2 database directory 2
    {other syscatspace, tempsacpe1 and userspace1 sms stuff}
    {files needed for database recovery and bookkeeping tasks}

    The node directory contains info regarding how and where remote systems or instances can be found as well

    You are the creator of your own destiny!

  4. #4
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    In DB2 LUW, when cataloging a node, it is a combination of the physical node (server) and the instance.

    The term node has other meanings in other contexts, especially in relation to parallel database configuration. A logical node may mean a partition, and a physical node may mean a server (which can have one or more logical partitions per physical node).
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

  5. #5
    Join Date
    Mar 2004
    Posts
    33

    Unhappy ???

    Hi all,

    thanks for all your help but it just gets me more confused. How about we
    first disregard the issue of partitioned database first in defining node and instance.

    MUCH MUCH THANKS
    ME

  6. #6
    Join Date
    May 2003
    Location
    USA
    Posts
    5,737
    In DB2 LUW, when cataloging a node, it is a combination of the physical node (server) and the instance.
    M. A. Feldman
    IBM Certified DBA on DB2 for Linux, UNIX, and Windows
    IBM Certified DBA on DB2 for z/OS and OS/390

  7. #7
    Join Date
    Mar 2004
    Posts
    448
    Take this as you are a client connecting to a server, so you sees a server(database host) as node providing you information about the instance and the database that is under that instance.so you catalog that node and starts taking to that database under that instance.
    So any times you want to interface to that database , you must go through that instance(that has its own service name/port that is using to listen to the client).

    The client also has its own instance, that provide you code/libraries to do all type of work as a client.

    Now you are at machine(local) that hosts a database,so you create a instance(infact a instance is nothing but links to various libraries of the same db2 code and various binaries).
    so if you want to connect to an instance you attached to it(attached is nothing more than attaching to shared structure that a running instance will have provided through its ipc daemon/listener).
    Once you attached to an instance, you ask that instance to connect me to that database(infact every local database is automatically catalog during the creation).

    Now in db2 terminology when you are at the local machines or mutiple machines, you can create partitions that are spread across mutiple physcial machines or as logical partitions at the same machine.These are all database partitions that are sharing the same instance and all the other things are unshared.In version 7 or earliar this database partition was known as node partition(infact all the commands the has node clause also work in V8)

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