We have a 3rd party application [Parametric Technology
Windchill] where a new module has been implemented which
copies in files into the database using DBMS_LOB.WRITE
The LOBSEGMENT has a CHUNKsize of 32K and the Database
BlockSize is 16K.
There are high waits on "direct path write". Queries
on V$SESSION_WAIT show
SID EVENT
---------- ----------------------------------------------------------------
P1TEXT P1
---------------------------------------------------------------- ----------
P2TEXT P2
---------------------------------------------------------------- ----------
P3TEXT P3
---------------------------------------------------------------- ----------
25 direct path write
file number 7
first dba 28684
block cnt 2
As the table and lobsegment have been pre-built by the application, I cannot now
modify it [in any case CHUNK is 32K already]. It is set to LOGGING, CACHE is NO and
PCTVERSION is 10.
The file system is fast enough. Copying in the same 1GB file with the unix "cp"
command took 1.5minutes. The DBMS_LOB.WRITE operation for the file took about 4 hours.
My only finding currently is that the size of the write, at 2 16K blocks, is too small.
Hemant K Chitale
http://hkchital.tripod.com
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Author: Hemant K Chitale
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