IDS Forum

Re: Re: after delete of rows is space immediately

Posted By: vze2qjg5@verizon.net
Date: Wednesday, 5 March 2008, at 12:15 p.m.

In Response To: Re: after delete of rows is space immediately avai (Martin Fuerderer)

True in concept, but there is an intermediate step. The pointer on each page remains pointing at the end of the page until enough rows have been deleted from the page and the engine determine that the page can be "compress"ed - all rows re-written starting at the beginning of the page - at which time the pointer is moved back into the page and the page is noted as a page with available space in the free list. The number of these operations can be seen in onstat -p output. So if are out of space in a table, and you delete one small row - no you will not be able to put one new small row in.

There are some holes in my understanding of this. 1) at what percentage of deleted rows is the page a candidate for compression? 2) Does this compression occur on the last delete or does something else happen? This last because I have seen pages compress even when there are no active deletes occurring - which implies that the engine waited until it read the page again to decide that it could be compressed.

j.

>From: Martin Fuerderer <MARTINFU@de.ibm.com>
>Date: 2008/03/05 Wed AM 10:52:56 CST
>To: ids@iiug.org
>Subject: Re: after delete of rows is space immediately .... [11492]

>Hi,
>
>the space is immediately available (after committing the
>delete) - for that same table, that is.
>
>This is because the deleted rows were in extents that have
>been allocated for that particular table. The space that was
>occupied by the deleted rows in these extents is free, but
>it remains in those extents and the extents remain allocated
>by the table.
>
>In short:
>- If you want to use the freed space for updates or
>inserts within the same table - no problem.
>- If you want to use the space elsewhere (other table
>or even other database), then you first have to
>re-organize the table to free the allocated extents.
>
>If necessary there should be lots of information available
>about table re-organization ...
>
>Regards,
>Martin
>--
>Martin Fuerderer
>IBM Informix Development Munich, Germany
>Information Management
>
>IBM Deutschland Entwicklung GmbH
>Chairman of the Supervisory Board: Martin Jetter
>Board of Management: Herbert Kircher
>Corporate Seat: Boeblingen, Germany
>Reg.-Gericht: Amtsgericht Stuttgart, HRB 243294
>
>ids-bounces@iiug.org wrote on 05.03.2008 17:44:32:
>
>> Hey everyone. Simple question about IDS 9.4. After a process does a
>delete of
>> X numbers of table rows........does the deleted rows become freespace
>> immediately? or is there some other action that needs to be done to make
>that
>> space immediately available? Thanks
>>
>>
>>
>
>*******************************************************************************
>> Forum Note: Use "Reply" to post a response in the discussion forum.
>>
>> See you at the IIUG Informix 2008 Conference
>> The Power Conference for Informix Professionals
>> April 27 - 30, 2008 Marriott Overland Park (Kansas City), Kansas
>> http://www.iiug.org/conf
>> Registration Now Open!!
>
>
>*******************************************************************************
> Forum Note: Use "Reply" to post a response in the discussion forum.
>
>See you at the IIUG Informix 2008 Conference
>The Power Conference for Informix Professionals
>April 27 - 30, 2008 Marriott Overland Park (Kansas City), Kansas
>http://www.iiug.org/conf
>Registration Now Open!!

Messages In This Thread

• after delete of rows is space immediately availabl
  WILL LANDSTROM -- Wednesday, 5 March 2008, at 11:44 a.m.
  • Re: after delete of rows is space immediately avai
    Martin Fuerderer -- Wednesday, 5 March 2008, at 11:52 a.m.
    • Re: after delete of rows is space immediately avai
      WILL LANDSTROM -- Wednesday, 5 March 2008, at 12:02 p.m.
    • Re: Re: after delete of rows is space immediately
      vze2qjg5@verizon.net -- Wednesday, 5 March 2008, at 12:15 p.m.
      • Re: Re: after delete of rows is space immediat....
        John Miller iii -- Wednesday, 5 March 2008, at 1:19 p.m.

IDS Forum is maintained by Administrator with WebBBS 5.12.