ODBC Server Installation and Management Manual

Managing the NonStop ODBC Server

HP NonStop ODBC Server Installation and Management Manual—429395-002

4-8

Configuring ODBC Datasources

By default, a NonStop ODBC datasource is set to Read-Write Standard, which allows

the application to perform general write operations (INSERT, UPDATE, and DELETE)

against the NonStop system, as well as UPDATE WHERE CURRENT OF operations

on a cursor. A severe performance penalty can result from running in this mode,

because the ODBC driver fetches only one row at a time from the server (each row is

returned in a separate network packet). The NonStop ODBC driver provides other

options that can be configured from the ODBC Administrator tool. These options are

set from Data Access Option, and are described following:

Read-Only Standard

In this mode, the driver requests that the NonStop ODBC Server send as many rows

as it can in a 4 KB block. The server actually sends the data back in 512-byte blocks,

sending each block as it becomes full. Some performance measurements taken with

this option have shown that performance can improve from a factor of 10 for very small

rows (four bytes) to a factor of three for large rows (200 bytes). With this option, the

application cannot perform any write operations. In this mode, data is returned in

bursts, 4KB at a time. A delay occurs between 4KB blocks as the driver requests the

server to send the next 4KB of data.

Read-Only Fast Transfer

In this mode, the driver requests that the server stream all rows back as soon as the

data is ready. The server actually sends the data back in 512-byte blocks, sending

each block as soon as it becomes full. Write operations are disallowed, and the

application cannot have more than one statement handle active at a given time. If an

attempt is made to open a second statement handle, the driver returns the error

“Unable to support concurrent statement handle execution,” SQLSTATE=H4700. This

transfer mode is the fastest, but might not be appropriate for a given application

because of the restrictions it imposes.

Custom Mode

When configuring a datasource using the ODBC Administrator, this mode allows you to

specify a more customized configuration. By choosing Custom, then clicking the

Parameters button, you are given the options described next.