ASA Database Administration Guide
  Connection and Communication Parameters
    Connection parameters

CommBufferSize connection parameter [CBSIZE]

Function 

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

Usage 

Anywhere

Values 

Integer

Default 

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

Description 

The CommBufferSize (CBSIZE) connection parameter specifies the size of communications packets, in bytes. The minimum value of CommBufferSize (CBSIZE) 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.

A larger packet size improves performance for multi-row fetches and fetches of larger rows. As each connection has its own pool of buffers, a large buffer size increases the memory usage. The application side uses four default-sized buffers per connection, and on the server side, there are two.

If CommBufferSize is not specified on the client, the connection uses the engine's buffer size. If CommBufferSize is specified on the client, the connection uses the minimum of either the engine's buffer size or the CommBufferSize value.

This corresponds to the SQL Anywhere Version 5 dbclient -p option. Using the -p option to set the CommBufferSize causes all clients which do not specify their own CommBufferSize, as well as all clients which specify a CommBufferSize larger than the engine's CommBufferSize, to use the size specified in the -p option.

Example 

• 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 ODBC Configuration dialog.