RBS tablespace
DBAsupport.com Forums - Powered by vBulletin
Results 1 to 8 of 8

Thread: RBS tablespace

  1. #1
    Join Date
    Jun 2000
    Location
    Maputo, Maputo-Mozambique
    Posts
    96
    Where does oracle write rollback information (undo information), if the rollback tablespace is taken to backup mode?
    any metalink or link references are wellcome.
    svrmgrl>alter tablespace RBS begin backup;

    Regards
    Alexandre
    In god i trust

  2. #2
    Join Date
    Jul 2000
    Posts
    243
    why do that? backing up a rbs tablespace?

  3. #3
    Join Date
    Jun 2000
    Location
    Maputo, Maputo-Mozambique
    Posts
    96
    I'm using a dynamic script that selects all tablespace from dba_tablespace. What i want to know is what happens when the RBS segment is in backup mode? the question is what happens and not why happens
    In god i trust

  4. #4
    Join Date
    Nov 2000
    Posts
    212
    Look for SYSTEM rollback segment(which can not be taken offline by the way). Here are some notes from oracle manuals:

    Note: No data can be inserted into any tablespace until the
    current instance has acquired at least two rollback segments
    (including the SYSTEM rollback segment).

    When a database is created, a single rollback segment named SYSTEM is
    created in the SYSTEM tablespace. You can create any objects in non-SYSTEM
    tablespaces, but you cannot write to them until you have created and brought
    online at least one additional rollback segment in a non-SYSTEM tablespace (for
    non-SYSTEM objects).


    An instance always acquires the SYSTEM rollback segment in addition to any other
    rollback segments it needs. However, if there are multiple rollback segments, Oracle
    tries to use the SYSTEM rollback segment only for special system transactions and
    distributes user transactions among other rollback segments. If there are too many
    transactions for the non-SYSTEM rollback segments, Oracle uses the SYSTEM
    segment.



  5. #5
    Join Date
    Dec 2000
    Location
    Ljubljana, Slovenia
    Posts
    4,439
    While RBS tablespace is in backup mode, SYSTEM rollback segment does not play any other role that it plays normaly. It does not have to, because nothing is different with normal rollback segments while their tablespace is in backup mode.

    The original question could pe rephrased like: "Where does Oracle write my inserts, updates and deletes on a specific table while its tablespace is in backup mode?" The answer is obvious: In the coresponding datafile(s)! (Almost) nothing is changed while tablespace is in backup mode. Data is still writen to its datafiles like any other time. It is the same with tables, rollbac segments, indexes,... - any kind of segments. The changed blocks are still written to the datafiles.
    Jurij Modic
    ASCII a stupid question, get a stupid ANSI
    24 hours in a day .... 24 beer in a case .... coincidence?

  6. #6
    Join Date
    Aug 2000
    Posts
    462
    jmodic,

    What does putting a TS into backup mode do to the tables/tablespace?


  7. #7
    Join Date
    Nov 2000
    Posts
    212
    see an article "IS RMAN REALLY WORTH THE TROUBLE?
    Tim Gorman, SageLogix, Inc." from EVDBT site.
    If can not find it, I can send it to you.

    In short the idea is that begin backup freeze datafile headers for SCN updates. Then backup is done of a datafile while it is modified by oracle (db blocks written into it)
    When need to restored that datafile, changes from redo logs are applied to datafile(restored one) starting from SCN frozen in datafile's header.
    To freeze datafile header, a global checkpoint is performed to flush buffers from memory.

  8. #8
    Join Date
    Aug 2000
    Posts
    462
    Very informative! Thanks.

    [url]http://www.evdbt.com/TD_Rman.pdf[/url]

    [Edited by kmesser on 03-08-2001 at 03:00 PM]

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •  


Click Here to Expand Forum to Full Width