RE: Poor performance on bulk transfer across db link -- wrapup

David,  

You may need to alter the TCP send & receive buffer sizes for getting the throughput out of your network.  

If the packet roundtrip time in your LAN is 1ms ( 0.001 sec ) and you want to achieve 40MB/sec transfer rate then your TCP sent/receive buffers must be at least 0.001 * 40 MB = 40 kB.  

In most OSes I've seen, the default TCP buffer sizes are usually very low ( tcp_xmit_hiwat = 8 kB in solaris for example ).  

On which OS and Oracle version are you on? Oracle 10g allows you to specify RECV_BUF_SIZE and SEND_BUF_SIZE for TCP connections in sqlnet.ora ( subject to OS level max buffer & tcp window settings ). If not on Oracle 10g, then you need to use OS specific settings.  

http://download-uk.oracle.com/docs/cd/B14117_01/network.101/b10775/performan ce.htm#i1007572  

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Regards,
Tanel Poder
http://blog.tanelpoder.com <http://blog.tanelpoder.com/>  

From: oracle-l-bounce_at_freelists.org [mailto:oracle-l-bounce_at_freelists.org] On Behalf Of David Aldridge
Sent: Friday, November 09, 2007 00:25
To: Oracle List
Subject: Re: Poor performance on bulk transfer across db link -- wrapup

Thanks to everyone who responded.  

We did a bunch of testing on changing SDU, but aren't able to change the MTU due to the impact on other production systems. Reducing the SDU to match the MTU produced no performance change. DB Links just seem to be problematic for performance, maybe due to something in our own environment, but our timeline doesn't give us the opportunity to investigate further..  

We're looking at other solutions -- transportable talespaces, in fact.  

Thanks again.

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http://www.freelists.org/webpage/oracle-l Received on Thu Nov 08 2007 - 23:26:11 CST