RE: impdp performance in 11.1 vs 11.2
- From: "Mark W. Farnham" <mwf@xxxxxxxx>
- To: <sethmiller.sm@xxxxxxxxx>, <rjamya@xxxxxxxxx>
- Date: Wed, 20 Aug 2014 20:44:22 -0400
I believe you said the same thing. One thread of index creation, but “each
index in parallel up to the degree of parallelism of the job.” The way I read
that is serially doing one index at a time at the parallelism of PX slaves
matching the parallelism of the job.
When under time pressure you can work around this by NOT having impdp do the
index creates. Arrange to have your biggest few tables loaded first and run the
index creation scripts in multiple threads table by table so you get some
drafting of the read part of index build because it has just been done into
cache. 11.2 plus this *MAY* mean a special table read job to avoid adaptive
direct read so the table does pump through cache and you avoid multiple
repetitive block cleanouts and multiple physical reads.
IF you have plenty of time, avoid this slippery slope toward CTD. (tm gaja).
From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] On
Behalf Of Seth Miller
Sent: Wednesday, August 20, 2014 6:55 PM
To: rjamya@xxxxxxxxx
Cc: mschmitt@xxxxxxxxxxxx; Oracle-List; Andy Wattenhofer
Subject: Re: impdp performance in 11.1 vs 11.2
Raj,
You may be thinking of an older version. This is from an 11.2 Oracle white
paper.
During export, when there are two or more worker processes, data and metadata
unloading proceed in parallel. Data Pump will also automatically build each
index in parallel up to the degree of parallelism of the job. The permanent
parallel degree of the index itself remains unchanged from its source value.
http://download.oracle.com/otndocs/products/database/enterprise_edition/utilities/pdf/datapump11gr2_techover_1009.pdf
Seth Miller
On Wednesday, August 20, 2014, rjamya <rjamya@xxxxxxxxx> wrote:
Index creation never runs in parallel worker processes, only data load can run
in parallel. Even metasata load/unload is run by a single worker process.
You will need to trace impdp to find why something is fast and slow. Google for
'expdp trace'.
I think even on 12.1 index creation is run by only one thread. It may use PX
slaves if index was originally parallel by only one worker thread does that
whilest others are idle.
Raj
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