Hi David, There are multiple TCP buffer size related parameters in Solaris, tcp_max_buf specifies the *maximum* TCP buffer size per socket, while tcp_xmit_hiwat sets the *default* size per socket. FTP may be bumping up its TCP send & receive buffer from its default, while Oracle is not. -- Regards, Tanel Poder http://blog.tanelpoder.com <http://blog.tanelpoder.com/> _____ From: David Aldridge [mailto:david@xxxxxxxxxxxxxxxxxx] Sent: Friday, November 16, 2007 20:56 To: tanel.poder.003@xxxxxxx; 'Oracle List' Subject: RE: Poor performance on bulk transfer across db link -- wrapup Sorry Tanel, missed your post. This sounds intriguing. I'll have to bounce it off the DBA's and network people. We're 100% Solaris 64bit here -- I'll have to checkup on the exact versions. The source db is 9.2 and the target is 10.2. Now would this affect Oracle Net in particular? If ftp achieves speeds an order of magnitude faster than Oracle NET does that still indicate that the buffer sizes are too low? Tanel Poder <tanel.poder.003@xxxxxxx> wrote: 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 -- Regards, Tanel Poder http://blog.tanelpoder.com <http://blog.tanelpoder.com/> _____ From: oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] 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.