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Re: Poor performance on bulk transfer across db link.

From: kathy duret <>
Date: Wed, 7 Nov 2007 11:36:27 -0800 (PST)
Message-ID: <>

If you are doing this on a regular basis you might want to set up Materialized views    

  This is what I do now.    

  The logs are on my 9i db and the views are on a 10g.    

  You really should be doing bulk transfers across a db link (IMHO)    

  It is faily fast to set up and I haven't had any issues    


David Aldridge <> wrote:

    I'm reading many hundreds of gigabytes from a 9iR2 database to a 10gR2 database through a database link. Some of the tables I am reading are rather wide, with average column lengths of between 500 and 850 bytes.    

  Performance appears to be constrained at the network level, with bandwidth in the order of 5Mbytes/sec on a gigabit network which demonstrates a 44MByte/sec ftp speed. There are no hops between the databases, with traceroute showing a direct server-to-server transfer.    

  I've been googling around and came across which explains the relationship between array size, row lengths, MTU, SDU etc..    

  Statspack on the source db shows the following for a one hour snapshot:    

  SQL*Net more data to client:
  1,336,548 waits
  0 timeouts
  2,885 total wait time
  2 Avg Wait (ms)
  2,069.0 waits/txn    

  So firstly, am I right in thinking that the default arraysize for database links is 15 rows?    

  If so, given that the MTU is 1500, the SDU is the default 2Kb, and the average row length is 600, is that data transfer rate of 4MBytes/sec surprising? If the MTU and SDU were adjusted skywards to the 15*600 range (say 10kb) would I expect to get much of an improvement?    

  Thanks in advance for any help -- I'm a network idiot.

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Received on Wed Nov 07 2007 - 13:36:27 CST

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