Freeing Unused Space via dbexport vs. onunload.
I am trying to make the distinction between how the
'dbexport/drop/recreate/dbimport' process clears out unused space vs.
how 'onunload/drop/recreate/onload' does it. Is there one that is more
efficient or do they both do the same thing (one on database, one on
tables)?
I was told by Informix tech support that the
'onunload/drop/recreate/onload' process would free unused space on a
particular table but wondered if the dbexport/import would do the same
thing but on the entire database.
Any feedback would be appreciated...
Mr. E
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In article <7katna$j32$1@nnrp1.deja.com>, Mr. E <tome@xyvision.com>
writes
>I am trying to make the distinction between how the
>'dbexport/drop/recreate/dbimport' process clears out unused space vs.
>how 'onunload/drop/recreate/onload' does it. Is there one that is more
>efficient or do they both do the same thing (one on database, one on
>tables)?
>
>I was told by Informix tech support that the
>'onunload/drop/recreate/onload' process would free unused space on a
>particular table but wondered if the dbexport/import would do the same
>thing but on the entire database.
>
>Any feedback would be appreciated...
>
onunload copies the pages for a table hence it will free
totally unused pages for 1 table.
dbexport unloads rows hence it free unused pages + reloads the
data into the least number of pages needed. i.e. partially
filled pages get coalesced...
>Mr. E
>
>
>Sent via Deja.com http://www.deja.com/
>Share what you know. Learn what you don't.
--
David Williams
"Mr. E" wrote:
>
> I am trying to make the distinction between how the
> 'dbexport/drop/recreate/dbimport' process clears out unused space vs.
> how 'onunload/drop/recreate/onload' does it. Is there one that is more
> efficient or do they both do the same thing (one on database, one on
> tables)?
>
> I was told by Informix tech support that the
> 'onunload/drop/recreate/onload' process would free unused space on a
> particular table but wondered if the dbexport/import would do the same
> thing but on the entire database.
Yes that will work just as well. Keep in mind that the fastest way to
recover space from a table and compress its extents is:
ALTER FRAGMENT ON TABLE mytable INIT IN dbspace; # or an appropriate
# fragmentation schemeThis can even be done into the same dbspace where the table already
resides!
Art S. Kagel