IBM CA/400 ODBC Driver Stops Receiving Large Query Responses (161772)

SYMPTOMS

When using the ODBC driver included with IBM Client Access/400 for Windows (V3R1M1) over the SNA Server 2.11 Windows 3.x client software, the ODBC driver may stop responding while receiving large query responses from the AS/400.

While receiving data, the SNA Server Windows 3.x client APPC interface returns the following error to the CA/400 ODBC RECEIVE_IMMEDIATE call:

   primary_rc   = 0x0001        (AP_PARAMETER_CHECK)
   secondary_rc = 0x00000006    (AP_INVALID_DATA_SEGMENT)

CAUSE

The IBM Client Access/400 ODBC driver passes a 32-bit address in the dptr "data pointer" parameter to the SNA Server Windows 3.x APPC RECEIVE_IMMEDIATE function. To protect against memory access violations, the SNA Server Windows 3.x APPC interface attempts to verify that the calling application has access to the data pointer and address range supplied to the RECEIVE_IMMEDIATE function. During this verification check, the address is treated as a 16-bit address, causing the top 16 bits to be truncated, in turn causing the verification to fail.

RESOLUTION

To resolve this problem, obtain the hotfix mentioned below. With this update applied, if Client Access/400 is used (indicated by setting CA400=YES in the [WNAP] section of the Win.ini initialization file), the SNA Server Windows 3.x client disables address verification checking as described above.

STATUS

Microsoft has confirmed this to be a problem in SNA Server version 2.11. This problem was corrected in the latest SNA Server version 2.11 U.S. Service Pack. For information on obtaining this Service Pack, query on the following word in the Microsoft Knowledge Base (without the spaces):

S E R V P A C K

A supported fix is now available, but has not been fully regression-tested and should be applied only to systems experiencing this specific problem. Unless you are severely impacted by this specific problem, Microsoft recommends that you wait for the next Service Pack that contains this fix. Contact Microsoft Technical Support for more information.