FIX: Access Violation Error on 16 MB Windows NT System

• Microsoft Visual FoxPro for Windows, version 3.0

SYMPTOMS

The "Access violation" error may occur when you use table buffering, transactions, and large amounts of data on a computer system that has 16 megabytes of memory and that is running Windows NT version 3.51. The error does not occur on sytems running Windows NT with 24 or 32 megabytes of RAM.

WORKAROUND

Use TABLEUPDATE() with smaller data sets. The Sample Code listed in this article fails when updating 4000 records at one time. However, reducing the number to 2000 cures the problem.

STATUS

Microsoft has confirmed this to be a problem in the Microsoft products listed at the beginning of this article. This problem was corrected in Visual FoxPro 3.0b for Windows.

MORE INFORMATION

Sample Code to Reproduce Problem

*-- Begin Code Example SET ESCAPE OFF SET TALK OFF SET FULL ON SET DELETED ON SET EXCLUSIVE OFF SET EXACT ON SET MULTILOCKS ON

CLOSE DATA ALL

IF !FILE( 'mydbc.dbc' )

    CREATE DATABASE mydbc
    OPEN DATA mydbc EXCLUSIVE
    CREATE TABLE mytable (keyfld n(10) PRIMARY KEY)
    CLOSE DATA ALL

USE mytable CALC MAX(keyfld) TO m.keyfld

IF CURSORSETPROP('buffering', 5 )

    ? 'table buffering enabled'

    FOR i = 1 TO 4000
        m.keyfld = m.keyfld + 1
            IF i % 100 = 0
                ? i, ' records added'
            ENDIF
            INSERT INTO mytable (keyfld) VALUES (m.keyfld)
    ENDFOR

    ? 'beginning transaction'
    BEGIN TRANSACTION
    ? 'transaction begun'

    IF TABLEUPDATE( .t. )
            ? 'table update succeeded'
    ELSE
            ? 'table update failed'
            =TABLEREVERT(.t.)
    ENDIF

    ? 'ending transaction'
    END TRANSACTION
    ? 'transaction ended'

NOTE: This has not been tested on computers that are running Windows for Workgroups or Windows 95 with 16 megabytes of RAM.