The database server determines the size of the buffer to send and receive data to and from the remote server by the following factors:
The database server calculates the row size by summing the average move size (if available) or the length (from the syscolumns system catalog table) of the columns.
You might be able to reduce the size and number of data transfers by using the FET_BUF_SIZE environment variable to increase the size of the buffer that the database server uses to send and receive rows to and from the remote database server.
The minimum buffer size is 1024 or 2048 bytes, depending on the row size. If the row size is larger than either 1024 or 2048 bytes, the database server uses the FET_BUF_SIZE value.
For more information on the FET_BUF_SIZE environment variable, see the IBM Informix: Guide to SQL Reference.