RE: Setting SDU and tcp.nodelay

  • From: "Roger Xu" <Roger.Xu@xxxxxxxxxxx>
  • To: <cemail_219@xxxxxxxxxxx>, <oracle-l@xxxxxxxxxxxxx>
  • Date: Wed, 27 Sep 2006 14:34:29 -0500

SDU specifies the size of the packets to send over the network. 
Ideally, SDU should not surpass the size of the maximum transmission unit 
MTU is a fixed value that depends on the actual network implementation used. 
Oracle recommends that SDU be set equal to MTU.

-----Original Message-----
From: oracle-l-bounce@xxxxxxxxxxxxx
[mailto:oracle-l-bounce@xxxxxxxxxxxxx]On Behalf Of J. Dex
Sent: Wednesday, September 27, 2006 2:07 PM
To: oracle-l@xxxxxxxxxxxxx
Subject: Setting SDU and tcp.nodelay

I want to try setting SDU for a 9207 database to see if it helps performance 
issues that we are having since moving a database to another location over a 
longer WAN (we have already eliminated other possible solutions).  I have 
read a couple of documents on Metalink but I am still not sure how to know 
what to set SDU too?   One doc said to set the SDU size as a multiple of the 
MSS but I am not sure how to tell what the Maximum Segment Size is.  Another 
doc indicated that if the default is 2K, to double that and set it to 4096 
bytes.  Has anyone else had to do this?  Any suggestions?

Also, are there any negative ramifications of having both tcp.nodelay and 
SDU set?

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