To Shadow or Not to Shadow, That's the question.

[Ronald Anusiewicz]

I'd like to know if creating and using shadowed database systems is worth the effort.
Obviously, there are a lot of variables that could come into play. Would anyone care to share their
thoughts and experiences?

I'm currently using shadowed databases, but I can sit in front of each machine.

Ron

[csda1]

Re: To Shadow or Not to Shadow, That's the question.

See these Network Optimization Tips

[Ronald Anusiewicz]

Re: To Shadow or Not to Shadow, That's the question.

Thank you Ira.

If I understand your article correctly, the increase in speed would be strickly by chance and very random. i.e. there would need to be more than one user attempting to open/load the same form or report, etc. at the exact same time. The more users you have, the greater the probability. However; unless your application has only one form, report, etc. and your have maybe 100 users all logged on to the application at the same time, there may not be any kind of a performance gain using a shadowed database. Once all the users have opened the form, optimization doesn't matter.

With today's gigabit network speeds, It sounds to me that network optimization is a lot of extra work for almost no gain.

[csda1]

Re: To Shadow or Not to Shadow, That's the question.

Thank you Ira.

If I understand your article correctly, the increase in speed would be strickly by chance and very random. i.e. there would need to be more than one user attempting to open/load the same form or report, etc. at the exact same time. The more users you have, the greater the probability. However; unless your application has only one form, report, etc. and your have maybe 100 users all logged on to the application at the same time, there may not be any kind of a performance gain using a shadowed database. Once all the users have opened the form, optimization doesn't matter.

With today's gigabit network speeds, It sounds to me that network optimization is a lot of extra work for almost no gain.

If someone is copying a large file, or doing a non-LQO query, or anything that uses a lot of bandwidth on the network, the request you make for a relatively small form load will collide with that and be interleaved in the network requests. But if everyone is just using Alpha, and doesn't start at exactly the same times, and doesn't run a ton of non-LQO searches, or copying of a lot of data, or jumping around a lot of layout loads and with a lot of users, and the network requests are kind of random, then your network probably is not maxing out, and your speed is not slowed by not doing shadowing.

But, it also doesn't hurt speed by doing shadowing (unless the network is faster than access to a local drive - which I have seen) except when everyone does a shadow refresh at the same time.

[Ronald Anusiewicz]

Re: To Shadow or Not to Shadow, That's the question.

Thank you Ira.

Ron

[DaveM]

Re: To Shadow or Not to Shadow, That's the question.

Being that most of the dealers where I have installs have other installs with many(some very heavy in bandwith appetite) using the same network as my app, I think I will stay completely with shadowed.

I just went over the v11 runtime pdf about a week ago and it seems it suggested shadowed tables. Maybe I am wrong?

[GMLMECH]

Re: To Shadow or Not to Shadow, That's the question.

We have a small network, with a server and 5 users and were running a shadow on four stations. Did not find the shadow to be that much of an effort.

Having said that, we moved away from the shadow on one computer about 3 months ago; can't remember what the reason was, and the speed increased significantly related to loading of forms

All computers are now off the shadow and everyone is happier.

Our network is not managed by anyone with any skill so perhaps it was a setup issue.

Larry

[Ronald Anusiewicz]

Re: To Shadow or Not to Shadow, That's the question.

I have shadowed my networked application only because it seems like the correct way to implement a networked application.
Yes, it's easy to do when one can sit down at each computer and set up shadowing and then create the shortcut.

The problem is when I need to give a CD disk to someone and have them install the application with shadowing and the correct shortcut. What further complicates this issue is when I have multiple different applications. The runtime documentation is very good, but editing the code for each application and testing each install is a lot of work, especially when the memory isn't what it use to be.

Anyways, I've attached the autoexec script that I use when opening the shadow database as outlined in the runtime documentation. I tried to make it user friendly as the developer can set the variables that follow through the script. My shadow folder structure is:

C:\program files (x86)\myapp\Shadow\myapp.adb

The script creates a startup file: myapp.startup which is used by my predefined shortcut.

Ron

[Allen Klimeck]

Re: To Shadow or Not to Shadow, That's the question.

Ron you shouldn't put your program into the "program files" folder. Your "program" is mostly "data" & it should be in a data folder of it's own. Windows permissions will cause you much grief in the "programs files" folder".

[DaveM]

Re: To Shadow or Not to Shadow, That's the question.

Ron,

Seems a lot of work for what you are doing. I don't worry about a drive letter. My apps(now all of them) are under c:\alda\my apps where the runtime is in the alda folder and the shadow is in my apps folder on the work station. Data is in a folder on the server as \\server\data\my app. My startup(bootstrap) autoexec gives the user a prompt for the name of the other computer(server) where the only thing the user needs to do is type in the name of the server. The rest of the path is already there.

I do send 2 disks: one for data on server and one for shadow setup. Or I send both on one disk. It just depends. Mostly my apps are downloaded off a website.

[martinwcole]

Re: To Shadow or Not to Shadow, That's the question.

I tested an app that is shadowed, non shadowed, and there was a significant difference in speed - the shadow was much much much faster. I guess it depends on the app. Since the program, shadowed, is on the workstation, and all the scripts, forms, etc. are also on the workstation, it is not reasonable to me that non-shadowed could be faster than shadowed. Although, maintenance would be much easier.

But for speed, if you have a good server, T/S or Citrix is the way to go.

[CALocklin]

Re: To Shadow or Not to Shadow, That's the question.

I don't do my installs the way any of the previous posters do because I allow my customers to install their server copy and workstation copies to any folder they want. However, I do warn them not to install any of them to any "Program Files" folder.

As for using a shadowed version on the workstation....

I agree that in many cases it won't make much apparent difference in speed because of today's much faster networks. But I still set up my workstation apps as shadowed apps. For one things, not using shadowing does tie up more network resources and I don't want my apps to be the source of someone else's problems. And, as Martin pointed out above, a non-shadowed application will run slower - just maybe not slow enough for the user to detect it. Also there are times when it has been nice to update a server copy to let my customer test the new version on the server while the other people continue using the old/established version until the new one has been "approved". (That last thing has been rare but when it has been done, sometimes it was by not setting up the automatic refresh but usually it was by sending them a test copy of the update that still had the old network optimize number. Once approved, a new copy was sent with the revised network optimize number.)

As far as the difficulty of installation goes, if a workstation is shadowed then the person installing it has to figure out where the server data is in order to set up the shadowing but if it isn't shadowed the person installing it has to figure out where the server data is in order to set up the icon. Wait! They both have to figure out where the server data is - so I don't really see the difference. OK, there are minor differences but it can still be a pain either way. The only way to avoid all workstation install issues is to first guarantee that every network will be mapped and/or named exactly the same way - good luck on that one - then force the user to install your application into specific folders.

[Ronald Anusiewicz]

Re: To Shadow or Not to Shadow, That's the question.

I haven't encountered any issues with using "Program Files" that I know of. Could someone give me some history here?

[Tom Cone Jr]

Re: To Shadow or Not to Shadow, That's the question.

Ronald, Ted Giles has been bird doggin' this more than anyone. I'll defer to his comments. My own take on this is that MS has been discouraging the use of executables that write data to the Program Files or Program Files (X86) directories for security reasons. If you install Alpha there and Alpha then has to write something there also you can have problems. How about it, Ted? Did I get close?

BTW, this last question probably should be in a separate thread, right?

[martinwcole]

Re: To Shadow or Not to Shadow, That's the question.

If you are running XP, no problem; I believe it is true after that by default (Vista, W7) will not let you write to those directories. If you have UAC down to lowest setting, may let you. Note that in V10 and later Alpha will use My Documents to write stuff to - like the shadow folder for example.