Shedding Some Light

Yep, we are getting close to the conference, but more companies are getting on board the already crowded Southwest Fox Conference sponsor bus. I want to introduce you to xSQL Software. These guys have some cool SQL Server tools and have become our newest Bronze sponsor.

One tool in particular is a tool I have been looking for for more time than I care to admit. I think their xSQL Builder tool is as close to the Stonefield Database Toolkit Update feature for SQL Server as any product I have looked at. I am hoping to cover this tool during my SQL Server Developer Toolkit session.

xSQL Software is providing several doorprizes to be given away during the conference. Very cool stuff.

I am glad to see there are some live bloggers at FoxForward so I can hear about sessions and things going on at the conference. I am occasionally getting an instant messages from people at the conference too, which makes me want to be there even more than I did before the conference started.

Sounds like things are going well and some fun is being had by all.

I even had something added to my DAFUG to-do list {g}. Tod, interested in coming to Detroit in the near future?

Looking for the inside story? Check here:
Dave Crozier (all the way from England)
Kevin Cully (how the heck does the organizer guy have time??)
Steve Bodnar (speaking at the conference)
Tod McKenna (speaking at the conference)

There are a couple of other bloggers hanging out and speaking too so I am looking forward to reading their observations and thoughts too.

Today I get to leak the cat out of the bag for a new “feature” of Southwest Fox: K.O.K.O.P.E.L.L.I.

What the heck is K.O.K.O.P.E.L.L.I.??

One Web description is:

“Kokopelli is one of the most intriguing and widespread images surviving from ancient Anasazi Indian mythology, and is a prominent figure in Hopi legends. The figure represents a mischievous trickster or the Minstrel, spirit of music. Kokopelli is considered a symbol of fertility who brought well-being to the people, assuring success in hunting, planting and growing crops, and human conception.”

Another description:

“Magical flute player, humpback or hump-backed flute player”

You see three Kokopelli characters on the Southwest Fox logo. But today I bring a different definition to you…

Knock Out Konference Orientation – Produce Elective Lecture Layout Interactively.

What?!?

Dave Aring (from Visionpace – owners of the VFP framework MaxFrame Professional) has created a new Visual FoxPro applet that assists you in selecting a schedule customized for you based on the choices and preferences you have for the session slots. The app is quite simple: pick your favorite three sessions in any one slot for the entire conference. The application then uses a magical algorithm to determine the best fit so you get as many of your favorite sessions as possible.

You pick your priorities for the slots, click on the Create Schedule button, and then the Print Schedule button to preview the results. The output can be printed and brought with you to Mesa. The printed schedule when folded on the lines provided should fit nicely in the badge holder we will provide when you register Thursday.

The applet comes complete with text Help, and an interesting approach with truly graphical Help. Dave even included a block out feature so you can schedule session blocks you plan on skipping. Maybe the boss wants you to attend a conference call or staff meeting, or you have a session to give in that slot (can you tell what three organizers asked for this enhancement request {g}), or you just want to play hooky and attend one of the less formal offline sessions that happen in the hallway.

You can try out different session priorities to get different results. If you already know the sessions you want to attend you can just make them your number one sessions and not pick the 2nd and 3rd, and your schedule can be printed out.

In the user acceptance testing phase of this app I found it picked 50% of the sessions I had slotted with the “Rick Schummer Method” to picking sessions. I think this is pretty good. I hope you download it and give it a try, if not to help pick some sessions, but just to see how Visual FoxPro applications can be created and not look like your typical VFP app.

For more details on the new tool, see Dave’s blog entry on the Visionpace blog.

Thanks Dave for putting this together in your spare time and for contributing it to Southwest Fox!

Only 43 days until we all meet in Mesa!

I wanted to follow up on the issue of Flushing Windows Cache in VFP 8, and some resolution for my client who you may recall is another developer.

This has been a very frustrating experience because VFP 8 is fundamentally not working in all cases and hardware configurations as one would expect with SET REFRESH. The data refreshes fine when pulled from my server, has failed on the C-drive of my XP machine, and works fine when run on my external USB drive. My client can reliably get it to fail on his Windows 2003 Server. Sure we have a workaround with RLOCK(), but you have to wonder why VFP 8 works as expected in some cases and not in others, and what potential problems do we have if RLOCK() reduces performance, or the technique does not resolve 100% of the problem.

So I had my client recompile the test applet in VFP 9 to see if the problem is reproducible in VFP 9. I know Microsoft is not going to develop a fix for VFP 8, but with VFP 9 SP2 in beta we might still have a chance to get something resolved if it is broken. It is definitely easier to go to tech support with a VFP 9 problem. Mind you, at the beginning of this journey I instinctively mentioned to my client how Microsoft introduced the FORCE FLUSH and how this interacts with the Windows API to get the changes to disk, so maybe they saw a problem with the SET REFRESH and worked to solve this in VFP 9.

Sure enough, my client recompiled his test applet in VFP 9 and all is well with the SET REFRESH. The test applet is showing the changes to the table in the second instance of the application in all the test configurations. So the good news (at least in this case) VFP 9 is more stable and reliable than VFP 8.

I think the recompile in VFP 9 with a complete system test is the best route to go anyway. It is just FORCEing his hand (sorry for the intentional pun) to make the move a little sooner than he hoped for in the scope of his project.

Just in case you are looking for VFP training and you are not on the Visionpace distribution list, here is a notification I received this evening:

The next VFP Boot Camp will be in Kansas City, Missouri, October 1-3, 2007

Registration ends on September 14, 2007 for the highly-acclaimed VFP Boot Camp. This event delivers three jam-packed days of solid, hands-on learning. From the fundamentals of VFP development through the very latest VFP 9.0 features, this boot camp is designed to quickly get your VFP skills up to speed. Attendees will receive a 500 page manual in both print and electronic format.

For more information visit http://visionpace.com/developereducation.html or email info AT visionpace DOT com. To register call 888-904-7900

The initial session schedule for Southwest Fox is posted! Please note that the organizers have reviewed it and passed it by the speakers, but it is still subject to change if we discover a flaw. This will be finalized over the next couple of weeks.

You may be wondering how did I get two 8:00am sessions?!? You think I would have some pull being one of the organizers, but no, Tamar thinks I am good enough to keep people awake on Saturday and Sunday morning (at least this is what I am telling myself {g}). Seriously, I am not really complaining because I don’t mind the first session of the day.

I went through the schedule a few weeks back and picked the sessions I would like to attend (knowing darn well I might not get to any of them) and I only had one I could not schedule. There are definitely some tough choices, but that is the idea. We packed this conference with lots of great sessions presented by some of the best minds available.

I have two recommendations to those who cannot see all the sessions they really have to see. One thing I am doing is seeing sessions in advance of the conference. Check out the Fox user groups around the country kind enough to let speakers test-drive the sessions before they might be ready for prime-time at the conference. I see the Detroit Area Fox User Group (my local group) and the Chicago FUDG already have presentations scheduled. I am sure other groups will be scheduling some soon. You can find some of the user group meetings on the Fox Wiki Upcoming Events page.

The other option is to bring a teammate or friend to the conference (yes there is still time to register and we are not sold out yet {g}). You can each see different sessions and later go over the material you learned to help the other person as you review the white papers from the session together.

Only 50 days until we meet in Mesa!

I have a customer who is a developer using VFP 8 so we cannot use the new FLUSH FORCE functionality.

Here is the observation. Simple form with a private datasession opens the table and displays the data in the standard grid. The table is one of your typical USER tables and it has a logical flag in it to show if a user is logged in or not. The management like to occasionally check to see who is logged in or not. SET REFRESH is set to 10, 10 so every 10 seconds VFP should be refreshing the local buffers.

I can load up the app on my Windows 2003 server and the form performs as expected. As I start instances of the EXE and login as different users I can see the Flags change to true once the grid is refreshed or I move through the records after the 10 seconds.

If I run the EXE on a Windows XP SP2 machine and run multiple instances of the EXE on the same machine I do not get the data refreshed. I have even seen where I run the same form in the same EXE instance set up its own datasession with the old data.

Now I know the private datasessions are doing a USE AGAIN which does not go out to disk and get a fresh buffer, and uses the current cache to set up the new workarea. I also know if we throw in a simple RLOCK() it will refresh the cache.

It would be nice if all the installs were on a real server, but some of the end users are in a peer-to-peer environment and this is causing problems with the refreshing of the data.

My question is: is there something in Windows where we can turn off the data caching? I have hunted everywhere and I cannot find anything. I am recalling reading some where that Window 2003 has this shut off by default, but XP does not, but I cannot find the source of the material I read. Obviously Windows is caching the data or the Fox Team would not have added the FORCE clause for the FLUSH command.

The app cannot be migrated to VFP 9 to take advantage of the FLUSH FORCE. My recommendation to date is to use the RLOCK() “workaround”, but understandably if the developer has a toggle of a setting in Windows he would save himself the time of updating 50 forms, performing a complete system test, and the time it takes to redeploy to all his customer locations.

I would appreciate any insight any of you might have.

UPDATE 08-Aug-2007 @10:28 PM: passed along from fellow VFP MVP Fred Taylor on where to set the Windows Write Caching…

“If you mean the disk write caching, in XP bring up a My Computer and right-click on the disk you want, then choose properties. Then under the Hardwaretab, select the actual disk device and then use the Properties button. Under the Policies tab, there should be a check box for write disk caching there.”

I appreciate the help Fred!

One of my customers who is a developer described a form he built with the following scenario:

1. Private Datasession, single DBF table
2. Load event method opens the table and runs a SQL-Select of all the records into a cursor
3. Display of the records in the cursor in a grid. Grid RecordSource is the name of the cursor.
4. Observes the data change in the grid when users are changing the data in the base table on other machines in the office.
5. There is not code to rerun the SQL-Select, and no timers on the form.

His question to me is: how the heck does this happen? Good question.

His assumption was that the cursor data was stagnant since he queried it from the base table into the temporary cursor. Initially I agreed with him and we both thought we were going crazy, but then I remembered something I observed many years ago.

When you perform a SQL-Select and the VFP data engine determines it can be Rushmore optimized, behind the scenes VFP creates a new workarea, which is the same as the open table in another workarea via the USE AGAIN, and applies a Rushmore optimized filter to the new workarea. In essence, the cursor is really passing through the raw table information in the grid he used to display the data. So changes made to the table by the other users in the system are reflected in the grid based in the settings of SET REFRESH.

At first we thought we were nuts, and I had to step through the debugger to ensure the grid was really bound to the cursor and not directly to the table.

One way to avoid this gotcha is to use the INTO CURSOR …. NOFILTER clause on the query. It will slow things down a bit since it is forcing the cursor to be written to disk, but you will not get the filtered table, you get a real stagnant cursor.

Hopefully you will remember this situation if you run into the weird and maybe unexpected behavior.