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  1. #1
    Join Date
    Sep 2006
    Location
    India-Bangalore
    Posts
    8

    Unanswered: Tablespace Doubt

    Hello,

    I have a doubt on Oracle Tablespace (TS)

    Tablespace Definition says : "A tablespace is a logical storage unit within an Oracle database. It is logical because a tablespace is not visible in the file system of the machine on which the database resides".

    My Question is:
    1. What is logical storage unit ?
    2. TS does not exist physically, but we have size allocated to the TS. it is totally confusing me. How can we allocate the size which does not exist physically.

    Thanks,
    Naren

  2. #2
    Join Date
    Jul 2003
    Posts
    2,296
    I think of physical and logical this way:
    Physical = what files you actually see on the server and operating
    system. You see a datafile located at c:\location\db\users.dbf
    That is a physical file. When you make a physical backup this file is being copied or backed up.

    Logical = anything that you only see once you login to the database. You select data from a table.
    That data is STORED in a physical datafile but can only be viewed from inside the database (logically).
    A "tablespace" needs a datafile assigned to it. You do not SEE the tablespace from the server/OS
    level but you CAN see the datafile. A logical backup would be a backup of all the DATA in a database.
    You could only recover the data by recreating a new database and importing that logical
    data (tables, rows, indexes, etc).

    A tablespace can have many physical datafiles assigned to it.
    So, maybe 3 datafiles of a size of 2G are assigned the USERS tablespace.
    This would give the USERS tablespace a size of 6G.

    In the old days of technology servers were sometimes limited to a maximum file size.
    So, by assigning 50 datafiles of 2G each Oracle could then have a tablespace with a size of 100G
    while the operating system thinks that all it has are 2G files which stay below the maximum size allowed.

    (hopefully I didn't fuck any of this information up)
    Last edited by The_Duck; 10-28-08 at 18:39.
    - The_Duck
    you can lead someone to something but they will never learn anything ...

  3. #3
    Join Date
    Oct 2008
    Posts
    82
    Hello narendran,

    ts is logical... where container is physical
    we are allocating space to containers...b'coz container consists of tables
    ts consists any number of containers....

    for example.... movie hall is logical.... chairs in hall is physical
    we are allocating space to chairs...

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