Re: Question regarding lob column
Date: Wed, 06 May 2009 16:00:12 -0800
The user was supposed to be deleting records older than 6 months, but that never happened. Now, 14 months later, after the tablespace has grown to 32G, they're ready to delete rows and want to see that the delete really does free up the space. I just want to be able to run a few queries to show them that the space really was made available.
I do expect that I will only need to do this once, then, as time goes by rows will get added, then they will run the purge job on a monthly basis. Hopefully, oracle will reuse the space made available by the deletes, instead of taking new extents, and we won't have to keep adding datafiles...we limit our datafiles to 2G each.
Jack van Zanen wrote:
> Delete does not free up space in the tablespace. It frees up space
> within the table that can quite possibly be reused.
> If you need to free up space within the tablespace you need to reorg the
> table, which is a waste of time if you are not going to be deleting
> regularly. It will simply grow again.
> 2009/5/7 Maureen English <sxmte_at_email.alaska.edu
> We have a table that has a lob column. The table is in tablespace
> A, the lob storage is
> in tablespace B (with an associated index).
> Every month a job runs and adds more data to this table, so we've
> had to add datafiles
> on a regular basis. Now the user wants to delete some data so we
> don't have to keep
> adding datafiles, but can reuse some of the space that's already
> been allocated to the
> So, I got a rowcount from the table before the user deleted
> anything, and I also got the
> bytes and extents values from dba_segments for the tablespaces.
> The user then proceeded to delete at least 1/3 of the rows in the
> table. When I did my
> queries again, the rowcount had changed as expected, but the bytes
> and extents values
> didn't change for the segments in dba_segments. There were 172
> extents before and there
> are 172 extents after the delete.
> Any ideas as to why no extents appear to have been freed up?
> We don't have Grid Control or EM available, so I can't see any
> pictures of space usage....
> - Maureen
> Jack van Zanen
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