Checking TCP Network Protocol Buffer for Direct NFS Client

Check your TCP network buffer size to ensure that it is adequate for the speed of your servers.

By default, the network buffer size is set to 1 MB for TCP, and 2 MB for UDP. The TCP buffer size can set a limit on file transfers, which can negatively affect performance for Direct NFS Client users.

To check the current TCP buffer size:

bash-4.0$ ndd -get /dev/tcp tcp_xmit_hiwater_max 
bash-4.0$ ndd -get /dev/tcp tcp_recv_hiwater_max

Oracle recommends that you set the value based on the link speed of your servers. For example:

bash-4.0# ndd -set /dev/tcp tcp_xmit_hiwater_max 10485760
bash-4.0# ndd -set /dev/tcp tcp_recv_hiwater_max 10485760