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HXTT DBF
update Memo field issue under Window Vista (HXTT DBF)
Frank Cheung
2008-04-01 12:18:08.0
Hi technical staff at HXTT,

I licenced the HXTT DBF recently. I'm testing the driver in a Java client under various Window environment. My development environment is JDeveloper 10G under Window XP. The driver works fine since early Feb when I first receive it.

Some of the Foxpro tables we have contains multiple Memo fields.

When the client is ran under Window 2000 or Window XP, it works fine. However when the client is ran under Vista (Business edition), after a record update, all the Memo fields in the record are consistently over-written by value of the last Memo field in the SQL statement or the last update query that has a Memo field. All other non Memo fields in the record were updated properly. Only the Memo fields were affected (under Vista). It seems during a SQL update the data in the Memo field is copied to all the Memo fields in the same record.

This seems odd as there's no issue like this under the older Window versions. I'm not sure what causes the difference in behavior under various Window versions.

The environment of my designs are:
1. Java client run under JRE version 6 update 5, HXTT DBF v4.0 driver
2. Foxpro 2.6 database (.DBF files) server in network drive.

As it happen under Vista it could be a Window issue.
I wonder if HXTT are awared of this issue and inform me if there is any work-around.

Should you need more information about the issue pls feel free to email me. Thank you.

Frank Cheung
Real Estate Division
Sauder School of Business
The University of British Columbia
Direct: (604) 822-2356 Fax (604) 822-1900
www.sauder.ubc.ca
Re:update Memo field issue under Window Vista (HXTT DBF)
Frank Cheung
2008-04-02 12:16:14.0
More discovery on the multiple Memo fields overwrite but no solution yet.

1. Driver characteristics: The Memo field over-write happen when the Java client ran under Vista using either preparedStatement & createStatement. It happen on both table insert and table update. Memo over-write happen even if I update individual Memo field with separate code block using newly instantiated Connection and Statement objects. (ie previous Connection & Statement objects are closed)

2. Compare .FPT files: By comparing the .FPT files of 2 identical table insert into a brand new database (I renamed the .dbf & .fpt files after the first insert, then copy a new set of .dbf & .fpt files for 2nd insert.) I found 2 things that were wrong. First, the Memo Header Record of the vista .FPT file were wrong. It's pointing to the wrong free block. It causes the 2nd & 3rd Memo field update to be written on the 1st memo block. Second, the Memo-Block-Header was wrong after being over-written that the length of memo (byte 04-07) were all 00s.

3. Not related to IPv6 setting in Vista. I check off the IPv6 setting in network. The Memo overwrite issue doesn't go away.


Developer friends, if your Java client can be ran under Vista and the database query update/insert multiple Memo field at the same time. Share with me if you experience this issue or not, and compare it with Win XP. Thanks a lot.

Frank

Re:Re:update Memo field issue under Window Vista (HXTT DBF)
HXTT Support
2008-04-03 03:36:29.0
Please download the latest package to see whether that issue disappear, although we haven't tried to recur your issue. If failed, I need some extra information:
1. Whether there are some Java clients access the same table from different hosts?
2. Whether that table is on a map network driver? The latest package was modified according to possible map bug of Vista.
3. What's your Foxpro 2.6 database (.DBF files) server.
Re:Re:Re:update Memo field issue under Window Vista (HXTT DBF)
Frank Cheung
2008-04-03 09:43:17.0
I downloaded the latest package 2 days ago and test it including the embedded driver. I get the same error.

So herq's the answer to your questions:
1. I hv 2 machines (XP for development/test, a Vista laptop for testing) on my desk. Both machines ran the same Java client program to access the same table when I manually click the update or query button on the applicaton. The database connection is closed after every query.
2. I'm the only person who use the test database Foxpro 2.6 table on a mapped drive connected thru Novell.
3. The .DBF files (Foxpro2.6) are on mapped drive G:\public\exameditortest\database\ex_bank2.dbf (.fpt & other files in same directory)

Hope this help. Thank you.
Re:update Memo field issue under Window Vista (HXTT DBF)
Frank Cheung
2008-04-05 20:55:21.0
I have additional info to question #3. The mapped drive G:\ is a Novell 5 server. (Did I mention Novell server to question #2?)

Frank
Re:Re:Re:Re:Re:update Memo field issue under Window Vista (HXTT DBF)
HXTT Support
2008-04-05 21:50:54.0
>Both machines ran the same Java client program to access the same table when I
> manually click the update or query button on the applicaton.
It seems that both of your client program will access the same table at the same time. You should try lockType=FoxPro connection property.
update Memo field issue under Window Vista (HXTT DBF)
Frank Cheung
2008-04-07 13:29:33.0
The latest driver solve the issue.

I download the newest driver (dated Apr 02) and found that it solves the issue! I downloaded the previous version (dated Mar 25) to verify the issue before I started this thread on Apr 1st. Therefore I thought I already have the latest version when you ask me to download again.

Though the 'lockType' properties is not related to the issue, I'll use this feature in the connection to avoid potential update conflict.

All evidence points to Vista which is to be blame. What have you done to the latest driver release? Is the issue Vista related? Is there a driver release tracking summary (what bug/feature is updated at which release..) that is available for review.

Anyway, thanks a lot for the help.

Frank


Re:Re:Re:Re:Re:Re:Re:update Memo field issue under Window Vista (HXTT DBF)
HXTT Support
2008-04-22 20:07:45.0
Sorry for omitting that thread.

>All evidence points to Vista which is to be blame. What have you done to the >latest driver release? Is the issue Vista related? Is there a driver release >tracking summary (what bug/feature is updated at which release..) that is >available for review.
I guess that Vista should have a bug on map driver for detecting cached file length, s so we have changed our code to avoid that bug. Since your issue disappear, I think we have found that key to skip that system bug:)

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