Re: The disk space used by a certain table??!!

The overhead per row and per block is not insignificant. Without having the formula at hand, I know in an Oracle 7 table out of 2048 bytes blocksize 1889 bytes are usuable at 10 percent free. As rows upon insertion are as far as know not split between blocks, there could be wasted space.
I just created a small table in PO 8i, after analysis it appeared the used space (again at 10 percent) is 1624 bytes out of 2048 bytes. However, I have only 6 rows at 49 bytes per row.
I'm going to do some further research I believe.

Regards,

Sybrand Bakker, Oracle DBA

<ibm_97_at_yahoo.com> wrote in message news:8it9pe$5os$1_at_nnrp1.deja.com...
> Thanks for your reply.
> But for my No.3 question, I mistyped. Actually the question I want to
> ask is:
> If the 'bytes' in 'dba_segments' is the allocated disk space by table
> 'tab', why is it much more than 'avg_row_len*num_rows'(even you can add
> more space for row header)? Since the pctfree is so small.
>
> Thanks again!
>
>
>
> In article <961622820.5673.0.pluto.d4ee154e_at_news.demon.nl>,
> "Sybrand Bakker" <postbus_at_sybrandb.demon.nl> wrote:
> > Answers embedded
> > <ibm_97_at_yahoo.com> wrote in message news:8ir8c7
 $nsu$1_at_nnrp1.deja.com...
> > > Hi, there:
> > >
> > > Oracle 8i for solaris 2.6
> > > table 'tab': pctfree is 5, pctused is 75.
> > > database block size is 8k.
> > >
> > > Analyae table 'tab':
> > > analyze table tab estimate statistics sample 20 percent;
> > >
> > > From the 'user_tables':
> > > blocks: 1754
> > > num_rows:62424
> > > avg_row_len: 210
> > >
> > > What does the 'blocks' mean in here?
> >
> > The number of used blocks (extrapolated, as you only sampled 20
 percent)
> > >
> > > From the 'dba_segments' get the corresponding info for this 'tab'
 table:
> > > bytes: 20971520
> > > blocks: 2560
> > >
> > > My questions:
> > >
> > > 1. what's the difference between the two 'blocks'?
> > The former is in use the latter is allocated
> >
> > > 2. what does the 'avg_row_len*num_rows' mean? Does it mean the real
 used
> > > disk space by the 'tab'?
> > No, this formula will not return the used space as the row overhead
 is not
> > included.
> >
> > > 3. If the 'bytes' in 'dba_segments' is the allocated disk space by
 table
> > > 'tab', why is it much more than 'avg_row_len'? since the pctfree is
 so
> > > small.
> > >
> > avg_row_len is the average length of an individual, single, row, not
 of all
> > rows. Hence it is normal to be small
> >
> > > THanks a lot!!
> > >
> > >
> > > Sent via Deja.com http://www.deja.com/
> > > Before you buy.
> >
> > Hth,
> >
> > Sybrand Bakker, Oracle DBA
> >
> >
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Thu Jun 22 2000 - 00:00:00 CDT