Oracle 10g RAC database TCP parameters on solaris 10

omarfarid
omarfarid used Ask the Experts™
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Please provide optimized TCP parameters on Soraris 10 (SPARC) for OLTP Oracle 10g RAC database for below TCP parameters

tcp_rexmit_interval_min
tcp_rexmit_interval_max
tcp_rexmit_interval_initial
tcp_ip_abort_interval
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Brian UtterbackPrinciple Software Engineer

Commented:
Generally you should leave these at the defaults. However, if you are on a closed LAN with very small round trip times they can be tuned to be more efficient. The latest kernel update patch for Solaris 10 already reduces the tcp_rexmit_interval_initial parameter from 3 seconds to 1 second. You could go down to 500ms, but I wouldn't go lower than that. On the same token, you could reduce the tcp_rexmit_interval_min to 200ms. You should never reduce the tcp_ip_abort_interval below 1 minute, but the abort interval doesn't affect the transaction efficiency anyway.
Top Expert 2007

Author

Commented:
Thank you blu, can you provide more info on how to tune these parameters? Is there a document covering their tuning?

currently, my servers parameters values are as below:

h1 (sun v480):
#########
tcp_rexmit_interval_min=400
tcp_rexmit_interval_max=60000
tcp_rexmit_interval_initial=1000
tcp_ip_abort_interval=300000


h2 (sun v480):
#########
tcp_rexmit_interval_min=400
tcp_rexmit_interval_max=60000
tcp_rexmit_interval_initial=1000
tcp_ip_abort_interval=300000

z1 (sun v490):
########
tcp_rexmit_interval_min=400
tcp_rexmit_interval_max=60000
tcp_rexmit_interval_initial=3000
tcp_ip_abort_interval=480000

z2 (sun v480):
########
tcp_rexmit_interval_min=400
tcp_rexmit_interval_max=60000
tcp_rexmit_interval_initial=1000
tcp_ip_abort_interval=300000

Oracle support said "these parameter depends on customer environment and can vary up the h/w , network topologies, switch etc" but did not give any guidelines on how to set them or what are the recommended values.

This is related to radius restarts and we are suspecting connectivity issue with the oracle RAC database
Principle Software Engineer
Commented:
As to how to tune them, you can look here for an example:

http://docs.oracle.com/cd/E19918-01/820-2488/ds-tcp-sol10/index.html

What to tune them to is trickier. The rexmit_initial affects how quickly retransmissions happen when there is no RTT calculated yet. Too small and you will start resending packets that haven't been dropped. Too large and the other side can timeout a connection before a retransmission occurs.

What problem are you trying to solve; what is the symptom? All of these relate to connections that are dropping packets, so shouldn't affect much unless there is congestion or routing problems.
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Top Expert 2007

Author

Commented:
As I said, we are facing radius server crashes and suspection is twards database. There is a firewall in between the database RAC servers and the RADIUS server.
Brian UtterbackPrinciple Software Engineer

Commented:
What I mean is, these prameters are dealing with the retransmissions of dropped packets at various stages of the connection. Is the problem you are experiencing related to dropped packets and aborted connections? Will faster or slower retransmissions help? Shorter or longer abort timeout?
Top Expert 2007

Author

Commented:
How to check if there are dropped packets on the servers themselves?
Brian UtterbackPrinciple Software Engineer

Commented:
You can use netstat to see the retransmission counters for TCP.
Top Expert 2007

Author

Commented:
Thanks for your support. The case is still open with Oracle

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