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

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 Received on Wed Jun 21 2000 - 00:00:00 CDT