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export dump
when we take a export dump with compress =y option, how does one get to know that the actual compression has taken place?
Sharmila
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OCP 8i
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When you export to dump file with compress=y, EXPORT utility modifies the INITIAL value of the table to be the sum of the current extents. So that means if the table has 50 * 10K extents filled, then the INITIAL extent when you IMPORT the data will be 500K.
Agasimani
OCP(10g/9i/8i/8)
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thanks , i very well know that this is what happens, but what i was wondering is that how do one come to know that such a option is used,, any query , DD views to tell us that compress =y has taken effect
Sharmila
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OCP 8i
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Last edited by bang_dba; 12-18-2002 at 06:37 AM.
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check dba_extents.bytes and compare with the older value.
By default compress=y
if u want to retain the old storage values say compress=no
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compress=y is a no no option
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Originally posted by sharmila
... but what i was wondering is that how do one come to know that such a option is used,, any query , DD views to tell us that compress =y has taken effect
AFAIK there is no DD views for this.
Giani
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Originally posted by pando
compress=y is a no no option
pando, please explain - tx
"The power of instruction is seldom of much efficacy except in those happy dispositions where it is almost superfluous" - Gibbon, quoted by R.P.Feynman
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Originally posted by DaPi
pando, please explain - tx
Oooh oooh! I know this one!
compress=y leads to tablespace fragmentation by having different sized extents created on import.
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if you understand well delete, truncate, segments and extents you will see why
if I have 100 extents with 1MB each but there are only 1MB real data what happens if I export with compress=y? I will get one 100MB extent 99% empty, if I use compress=n what happens? I get 1extent of 1MB, I saved 99MB
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