Is there an easy way to limit the number of users who are on a shared
database (non-c/s?). The only thing I've come up with is to force the
user to log in, and then if user limit has been exceeded, prevent the
new user from logging in, or log out oldest user. Is there an easier
way? (I just don't want 20 users logging into my application that is
meant for 1 or 2 users.)

TIA

Dave

Dave


If its a matter of not having to have the user log in why not just use a "silent login". You don't need user id or password, just use semaphore flags.

The way I do it is on logon set the semaphore against the users table (any table could be used) having first checked that a limit has not been exceeded. Then on closing the app I

 if uLck <> -1 then DM.Users.UnlockSemaphore(uLck);

So in your case when they start the app use SetSemaphore

Dead easy. But will not work in ElevateDB (I think Tim said)

All you need is somewhere to hold the allowed number of users.



Roy Lambert

procedure THHForm.SetSemaphore(uLim: integer);
var
SaveLockRetryCount: Integer;
SaveLockWaitTime: Integer;
begin
SaveLockRetryCount := Session.LockRetryCount;
SaveLockWaitTime := Session.LockWaitTime;
try
 Session.LockRetryCount := 0;
 Session.LockWaitTime := 0;
 uLck := 1;
 while (uLck <= uLim) and (not DM.Users.LockSemaphore(uLck)) do Inc(uLck);
 if (uLck > uLim) then begin
  MessageDlg('The maximum number of users permitted has been exceeded. Please contact your supplier', mtInformation, [mbOk], 0);
  Application.Terminate;
 end;
finally
 Session.LockRetryCount := SaveLockRetryCount;
 Session.LockWaitTime := SaveLockWaitTime;
end;
end;

Roy,
   Thanks for the code example. What happens if the user's machine reboots
without a graceful exit? How long will the semaphore lock be held?
There's two types of computer reboots to consider: the user accessing
the database over the lan, and the user accessing the data locally. Will
your semaphore locking handle reboots?

TIA
Dave

Dave


>    Thanks for the code example. What happens if the user's machine reboots
>without a graceful exit? How long will the semaphore lock be held?
>There's two types of computer reboots to consider: the user accessing
>the database over the lan, and the user accessing the data locally. Will
>your semaphore locking handle reboots?

I've just tried it resetting a test app in the IDE, and ctrl-alt-del'ing the test app and it seems to work. I'm not going to take a hammer to my PC to really try it out

Roy Lambert

Roy Lambert wrote:

> Dave
>
>
>
>>    Thanks for the code example. What happens if the user's machine reboots
>>without a graceful exit? How long will the semaphore lock be held?
>>There's two types of computer reboots to consider: the user accessing
>>the database over the lan, and the user accessing the data locally. Will
>>your semaphore locking handle reboots?
>
>
> I've just tried it resetting a test app in the IDE, and ctrl-alt-del'ing the test app and it seems to work. I'm not going to take a hammer to my PC to really try it out
>
> Roy Lambert
>

Roy,
    Great, thanks for testing it out. I'll give it a whirl.

Dave

Roy,

< Dead easy. But will not work in ElevateDB (I think Tim said) >>

EDB allows you to set the number of licensed users per configuration even
with local apps.

--
Tim Young
Elevate Software
www.elevatesoft.com