Re: segment size

richchri_at_erols.com (richie) wrote in message news:<9a436674.0310300618.35831e0b_at_posting.google.com>...
> Running oracle 9 and 8i on linux platform (redhat 8). Just a general
> oracle question. A segment is made up of extents. In our case the
> initial and next extent size is 1M. One of our segments for example
> has lets say 800 extents (From the "extents" field from dba_segments
> or user_segments for that user). So if segments are made up of extents
> and we have 800 of them at 1M each. Shouldn't the size of the segment
> (the sum of the "Bytes" field for that segment_name from the
> dba_segments table) total 800 Mbs? I get a almost 300Mb? Where's the
> other 500Mbs of space? Does that mean this is lost in fragmented
> space? So if I rearrange things and everything gets packed nicely with
> no gaps do I get back
> the missing 500MBs? Or do these values mean something else that I'm
> not aware of?
>
> thanks.

OEM has a good visualization and tabular format of segments. Go into the console and select your database --> storage --> tablespaces --> your tablespace, right click on it and select Show Tablespace Map. Click on the segment name and it lights up on the map. Then drop down View and select Show Tabular Map and you can see the size of each segment, as well as the block ID.

If you use locally managed tablespaces on 8i, don't get too freaked out about fragmentation. If you don't, google this group for LMT.

jg

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