Re: export/import compress?

In article <3ig5ou$fgs_at_instasrv.admin>, ccisaac_at_mtu.edu (Chuck Isaacson) writes:
>From: ccisaac_at_mtu.edu (Chuck Isaacson)
>Newsgroups: comp.databases.oracle
>Subject: export/import compress?
>
> I just completed a full export of one instance and a
>full import to another. A side benefit to this exercise to my way
>of thinking was that all tables would be compressed to one extent
>in the new instance.
>Was I surprised to see 16 tables, some large(120,000,000 bytes),
>some small (196000 bytes) with multiple extents.
>A check of the source instance shows 28 tables with multiple extents
>most of which are not multiple on the new instance.
>
> The process was as follows:
>1 multiple exports as system for each owner rows=y indexes=y separate .dmp
> (default is compress=y)
>2 export as system full=y rows=n (default is compress=y)
>3 create new instance
>4 import as system full=y rows=n - to recreate all tables
>5 multiple imports as system for each of the owners rows=y indexes=y using
> the separate .dmp files from step 1
>
>Step 1 was run with more than 1 export executing at a time
>Step 5 was run with more than 1 import executing at a time
>
>Oracle level 6.0.37
>
>There were more than 1500 tables involved so this is a small percentage
>but I am confused as to why export did not compress all tables. Can
>anyone provide an explanation?
>
>Thanks
>Chuck ccisaac_at_mtu.edu
>
>
>
 Just a wild thought - were these tables originally created with  MIN_EXTENTS > 1 ?  Check out the view DBA_SEGMENTS for this information.

 You can obtain the original CREATE TABLE statements by using  INDEXFILE=name on another import of the full export along the lines of

   imp system/pass file=your_export indexfile=your_file full=y

  Check the file produced for the required tables and you will see exactly   the size and number of extents that the export specified.

  I'm curious at to why you did multiple user exports then a system export

• was it just to speed up the export/import process time and if so have you any idea of the savings (if any) that it produced ?

  Hope this is of some small help

  Ian
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