Sets the maximum size of communication packets, in bytes.

Usage

Anywhere

Values

Integer [ k ]

Default

If no CommBufferSize value is set, the CommBufferSize is controlled by the setting on the server, which defaults to 7300 bytes on all operating systems except Windows Mobile. On Windows Mobile, the default is 1460 bytes.

Remarks

The CommBufferSize (CBSIZE) connection parameter specifies the size of communication packets, in bytes. Use k to specify units of kilobytes. The minimum value of CommBufferSize is 500 bytes, and the maximum is 16000 bytes.

The protocol stack sets the maximum size of a packet on a network. If you set the CommBufferSize to be larger than that permitted by your network, the communication packets are broken up by the network software. The default size is a multiple of the standard ethernet TCP/IP maximum packet size (1460 bytes).

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.

See also

• How connection parameters work
• Connection parameter tips
• Tuning TCP/IP performance
• -p server option

Example

To set the buffer size to 1460 bytes:

...
CommBufferSize=1460
...

Alternatively, you can set this parameter by entering its value in the Buffer Size text box on the Network tab of the ODBC Configuration For SQL Anywhere 11 window.