SMON coalesce
DBAsupport.com Forums - Powered by vBulletin
Results 1 to 7 of 7

Thread: SMON coalesce

Hybrid View

  1. #1
    Join Date
    Feb 2002
    Posts
    267
    hi folks,

    Why does SMON coalesces free space only when we set the PCTINCREASE>0.
    what is the logic behind this.

    Regards
    sonia

  2. #2
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
    Posts
    3,938
    SMON wakes up every 5th minute and checks for tablespaces with default pctincrease != 0. However, SMON might not coalesce all free space every time it runs.

    Coalescing means gathering together small chunks of free space into larger chunks of free space. This hopefully answers your 2nd question.
    Oracle Certified Master
    Oracle Certified Professional 6i,8i,9i,10g,11g,12c
    email: ocp_9i@yahoo.com

  3. #3
    Join Date
    Nov 2000
    Location
    greenwich.ct.us
    Posts
    9,092
    Originally posted by Sonia
    hi folks,

    Why does SMON coalesces free space only when we set the PCTINCREASE>0.
    what is the logic behind this.

    In theory, if PCTINCREASE = 0, you won't need to coalesce because your extents will be equally sized. Therefore, they can be reused without being coalesced into bigger chunks.
    Jeff Hunter
    marist89@yahoo.com
    http://marist89.blogspot.com/
    Get Firefox!
    "I pledge to stop eating sharks fin soup and will not do so under any circumstances."

  4. #4
    Join Date
    Feb 2002
    Posts
    267
    Thanx Jeff

    U have got the point there.

    Regards
    sonia

  5. #5
    Join Date
    Oct 2000
    Location
    Charlotte, USA
    Posts
    330
    yes..remember the next extent calculation formula
    next extent=next extent(1+pctincrease/100)...
    Thanks.
    Thanigaivasan

  6. #6
    Join Date
    Apr 2002
    Posts
    4
    when you insert data into extents, DBWR looks for an extent which is bigger than the current extent (if PCTINCREASE > 0). If SMON doesn't coalesce the free space into larger extents, data never gets inserted into those extents and the tablespace gets fragmented.

  7. #7
    Join Date
    Jun 2001
    Location
    Helsinki. Finland
    Posts
    3,938
    Originally posted by rameshk
    when you insert data into extents, DBWR looks for an extent which is bigger than the current extent (if PCTINCREASE > 0). If SMON doesn't coalesce the free space into larger extents, data never gets inserted into those extents and the tablespace gets fragmented.
    The space allocation in Oracle is not that simple, it depends on several things: if the request for space would occupy more or less than 5 blocks, if Oracle needs to split the extent or find an exact match and on the order of the listed free extents in the SGA.



    Oracle Certified Master
    Oracle Certified Professional 6i,8i,9i,10g,11g,12c
    email: ocp_9i@yahoo.com

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