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Home -> Community -> Mailing Lists -> Oracle-L -> RE: Export of IOT very slow
Do you have any lobs? There has to be some reason that is forcing it to
use the sequential reads.
The execution path is usually Fast Full Scan that uses scattered reads.
Waleed
-----Original Message-----
From: Rick Stephenson [mailto:RStephenson_at_Ovid.com]=20
Sent: Wednesday, May 26, 2004 5:35 PM
To: oracle-l_at_freelists.org
Subject: RE: Export of IOT very slow
There is currently no overflow segment assigned to this IOT.
Thanks,
Rick Stephenson
-----Original Message-----
From: Khedr, Waleed [mailto:Waleed.Khedr_at_FMR.COM]=20
Sent: Wednesday, May 26, 2004 3:17 PM
To: oracle-l_at_freelists.org
Subject: RE: Export of IOT very slow
Interesting!
Could it be a result of bad settings for the overflow segment (you have
an overflow segment that requires a single block visits similar to the
chained rows situation for tables)?
Waleed
-----Original Message-----
From: Rick Stephenson [mailto:RStephenson_at_Ovid.com]=3D20
Sent: Wednesday, May 26, 2004 5:04 PM
To: oracle-l_at_freelists.org
Subject: Export of IOT very slow
Why does an IOT only allow for 1 block read at a time to extract data
during
an export. I have an IOT with 250 Million rows that takes 24 hours to
export, whereas, I have a heap table with 12 million rows that takes 6
minutes to export. If I extrapolate that out, the heap table would take
roughly 2 hours to finish with 250 million rows. I decided to trace the
processes and noticed that the IOT export will only read 1 block at a
time,
whereas the heap reads in 16 blocks at a time. Is there a way to force
the
"sequential" read to grab 16 blocks at a time?
=3D20
I am running EE 9.2.0.3 on Solaris 2.8.
=3D20
Trace file for IOT:
WAIT #0: nam=3D3D'db file sequential read' ela=3D3D 5828 p1=3D3D15 =
p2=3D3D509603
=3D
p3=3D3D1
WAIT #0: nam=3D3D'db file sequential read' ela=3D3D 16070 p1=3D3D17 =3D p2=3D3D1063439 p3=3D3D1
WAIT #0: nam=3D3D'db file sequential read' ela=3D3D 13220 p1=3D3D16 =
p2=3D3D39872
=3D
p3=3D3D1
=3D20
Trace file for Heap:
WAIT #3: nam=3D3D'db file scattered read' ela=3D3D 1810 p1=3D3D27 =
p2=3D3D32645 =3D
p3=3D3D16
WAIT #3: nam=3D3D'db file scattered read' ela=3D3D 1648 p1=3D3D27 =
p2=3D3D32661 =3D
p3=3D3D16
WAIT #3: nam=3D3D'db file scattered read' ela=3D3D 1866 p1=3D3D27 =
p2=3D3D32677 =3D
p3=3D3D16
=3D20
Thanks for your help,
=3D20
Rick Stephenson
=3D20
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