Expert Oracle Exadata - Parent Directory

CHAPTER 13 MIGRATING TO EXADATANow all connections between the source server and that subnet would request both send andreceive socket buffer size 4 MB, but connections using other routes would continue using default values.Note that this route change setting isn’t persistent across reboots, so you would need to get thesysadmin to add this command in a Solaris (or SMF service) startup file.Before you change any of these socket buffer setting at the O/S level, there’s some good news if yoursource database is Oracle 10g or newer. Starting from Oracle 10g, it is possible to make Oracle request acustom buffer size itself (up to the tcp_max_buf limit) when a new process is started. You can do this bychanging the listener.ora on the server side (source database) and tnsnames.ora (or the raw TNSconnect string in database link definition) in the target database side. The target database acts as theclient in the database link connection pointing from target to source. This is well documented in theOptimizing Performance section of the Oracle Database Net Services Administrator’s Guide, section“Configuring I/O Buffer Size.”Additionally, you can reduce the number of syscalls Oracle uses for sending network data, byincreasing the Oracle Net Session Data Unit (SDU) size. This requires either a change in listener.ora orsetting the default SDU size in server-side sqlnet.ora. Read the Oracle documentation for more details.Here is the simplest way to enable higher SDU and network buffer in Oracle versions 10g and newer.Add the following line to the source database’s sqlnet.ora:DEFAULT_SDU_SIZE=32767Make sure the source database’s listener.ora contains statements like the following example:LISTENER =(DESCRIPTION_LIST =(DESCRIPTION =(ADDRESS = (PROTOCOL = IPC)(KEY = EXTPROC1521))(ADDRESS =(PROTOCOL = TCP)(HO/ST = solaris01)(PORT = 1521)(SEND_BUF_SIZE=4194304)(RECV_BUF_SIZE=1048576))))The target Exadata server’s tnsnames.ora would then look like this example:SOL102 =(DESCRIPTION =(SDU=32767)(ADDRESS =(PROTOCOL = TCP)(HO/ST = solaris01)(PORT = 1521)(SEND_BUF_SIZE=1048576)(RECV_BUF_SIZE=4194304))(CONNECT_DATA =(SERVER = DEDICATED)434