CommBufferSize connection parameter [CBSize]

To set the maximum size of communication packets, in bytes.

Anywhere

Integer

If no CommBufferSize value is set, the CommBufferSize is controlled by the setting on the server, which defaults to 1460 bytes.

The CommBufferSize parameter specifies the size of communications packets, in bytes. The minimum value of CommBufferSize is 300, and the maximum is 16000.

The protocol stack sets the maximum size of a packet on a network. If you set CommBufferSize to be larger than that permitted by your network, the largest buffers are broken up by the network software. You should set the buffer size to be somewhat smaller than that allowed by your network, because the network software may add information to each buffer before sending it over the network. The default of 1460 allows an ethernet packet to be completely filled when using TCP/IP.

A larger packet size may improve performance for multi-row fetches and fetches of larger rows, but it also increases memory usage for both the client and the server.

If CommBufferSize is not specified on the client, the connection uses the server's buffer size. If CommBufferSize is specified on the client, the connection uses the CommBufferSize value.

Using the -p database server option to set the CommBufferSize causes all clients that do not specify their own CommBufferSize to use the size specified by the -p database server option.

To set the buffer size to 400 bytes:

...
CommBufferSize=400
...

Alternatively, you can set this parameter by entering its value in the Buffer size text box of the Network tab of the connection window.