Re: File size difference between table in database and exported file

Jerome Moinet wrote:

> Could there be a reason for the big diference between a table size in
> database and the size of the exported file ?
>
> table size : 1.8 Gb (select bytes from dba_segment where segment_name = T1)
> and (select blocks from dba_tables where table_name = T1)
> exp user_at_database file=F1 table=T1 direct=y raws=y
> exported file : 2.43 Gb (ls -l F1 | awk {'print $5i/1048576 " Mo"'}
>
> Oracle version 8.0.6
> OS AIX 4.3.1
>
> Oracle support don't have any answer to this.

I've quite some crap in the answers offered, like if compress has anything to do with this.
First of all, bytes in dba_segments is bytes allocated, not used. Create an empty table, run your select and you'll see what I mean. Basically, the difference is even larger than what you think! Secondly, export is a portable format, and does not compress stuff like numeric data as well as Oracle can internally. In other words, data in the database takes less space that in an export file. Third, but this does not explain all the difference, there's overhead in the export file, like version, user, options used, and all the storage. Rum imp with the indexfile option, or just browse the export file (not recommended on a 2.3G file, tho!)
--
Met vriendelijke groet/kind regards,

Frank van Bortel
Technical consultant Oracle Received on Tue Mar 07 2000 - 17:27:38 CST