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Don Burleson Blog 







Oracle UDP Tips

Expert Oracle Database Tips by Donald BurlesonApril 22, 2015


Question:  How is the User Datagram Protocol (UDP) different than TCP/IP network protocol?

Is UDP defined for any database being designed or just for Data warehouse?

What all should be covered in the UDP configuration for an Oracle system?

Answer:   UDP is stateless, and you DO NOT want to use UDP for Oracle system where data integrity is an issue.  UDP is available on Linux, AIX, Solaris and HP/UX, and other OS platforms.  

Overall, the vast majority of Oracle databases use TCP/IP, because UDP does not have built-in hand-shake dialogues.  This means that UDP does not have the same data integrity and reliability and serialization as TCP/IP.  With UDP there is no guarantee that your packet will arrive at the destination and no mechanism for notifying you of a network failure!  Also, UDP is not serialized, so out-of-order transmission is possible.  

So, why choose UDP?  If you are on a super-reliable network where you have zero lost packets possibilities then you may choose UDP because it is far faster than TCP/IP, primarily because there is no overhead in establishing a handshake connection.  UDP is stateless.

UDP Parameters for AIX  

However, UDP is far faster than TCP/IP, so the UDP protocol is used for high impact communications areas such as domain name servers (DNS) UDP for AIX:  

In AIX, you can adjust the UDP kernel settings with the network options (?no?) command, which can alter the udp_sendspace and udp_recvspace parameters.  To enable UDP on AIX for Oracle, you set the following UDP parameters:

  •  udp_sendspace:  Set udp_sendspace parameter to [(DB_BLOCK_SIZE *DB_FILE_MULTIBLOCK_READ_COUNT) + 4096], but not less than 65536.

  • udp_recvspace:  Set the value of the udp_recvspace parameter to be >= 4 * udp_sendpace.  The value of the udp_recvspace parameter should be at least four to ten times the value of the udp_sendspace parameter because UDP might not be able to send a packet to an application before another packet arrives.  To determine the suitability of the udp_recvspace parameter settings, enter the following command:

         netstat -s | grep 'socket buffer overflows?

  •  sb_max:  If required, set the sb_max parameter (default value is 1048576) to a higher value because sb_max must be greater than udp_recvspace

UDP Parameters for Solaris

To enable UDP in Solaris for Oracle, initialize the following UDP kernel parameters:

  •  udp_xmit_hiwait:  The udp_xmit_hiwait parameter defines the default maximum UDP socket datagram size and is related to udp_max_buf.

  • udp_recv_hiwait:  The udp_recv_hiwait parameter specifies the default maximum UDP socket receive buffer size.

  • udp_max_buf:  The udp_max_buf parameter determines the size of the OS send and receive buffers for a UPD socket.  


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