Concurrent Processing of Client/Server App 
Author Message
 Concurrent Processing of Client/Server App

I have developed a 3 tiered , VB6,  Access 97 Db, application using
disconnected recordsets under ADO 2.1

When running the application in Windows 98 ,the DB component is an
ActiveX.exe which runs all the time.

In the initial test the first two tiers reside on the Work Stations

When the application starts up, a lot of  tables are read to load into the
Workstation.  Data that is used frequently is loaded into various Class
Modules and arrays

If two users start up their Work Stations at about the same time, we get an
Error 91: Object variable or with block variable not set

This happens when Vb tries to execute eg
    Set rs = Connect.Execute "Select......",  , adCmdText

I can see that I could use the Error Handler to pause and  execute the above
line until the DB is free.

Because Erro 91 can arise form other situations this approach does not
appeal.

Can anyone suggest where I might find some reference material on the
Conflict problem or suggest an alternative solution

Regards

Merv Couper



Fri, 03 Sep 2004 10:24:30 GMT  
 Concurrent Processing of Client/Server App
Hi,

I think that your Connect variable is not initialized. You
need to debug your code to see what is going on. It is
difficult to sy anything particular. In case of out-of-
process ActiveX (like in your case) you should be carefull
if you ActiveX used by many users. If your tier developed
as multiuse, then all clients will use same copy of
running component. In case of singleuse design each user
will have it's own copy of component. So you will have
diffrenet behaviour, depending on design of ActiveX

Val

Quote:
>-----Original Message-----
>I have developed a 3 tiered , VB6,  Access 97 Db,
application using
>disconnected recordsets under ADO 2.1

>When running the application in Windows 98 ,the DB
component is an
>ActiveX.exe which runs all the time.

>In the initial test the first two tiers reside on the
Work Stations

>When the application starts up, a lot of  tables are read
to load into the
>Workstation.  Data that is used frequently is loaded into
various Class
>Modules and arrays

>If two users start up their Work Stations at about the

same time, we get an
Quote:
>Error 91: Object variable or with block variable not set

>This happens when Vb tries to execute eg
>    Set rs = Connect.Execute "Select......",  , adCmdText

>I can see that I could use the Error Handler to pause

and  execute the above

- Show quoted text -

Quote:
>line until the DB is free.

>Because Erro 91 can arise form other situations this
approach does not
>appeal.

>Can anyone suggest where I might find some reference
material on the
>Conflict problem or suggest an alternative solution

>Regards

>Merv Couper

>.



Fri, 03 Sep 2004 20:43:07 GMT  
 Concurrent Processing of Client/Server App
Thanks Val for comments

I already test the initiation of the connection and this is OK

I have experimented with the ADODb WillExecute event, which seems to work
OK.
However  it is a lot simpler to just use the Error 91 to initiate a For Next
Loop with a random Number generator to execute the recordset at random times
until the recordset executes

Thanks again

Merv Couper


Quote:
> Hi,

> I think that your Connect variable is not initialized. You
> need to debug your code to see what is going on. It is
> difficult to sy anything particular. In case of out-of-
> process ActiveX (like in your case) you should be carefull
> if you ActiveX used by many users. If your tier developed
> as multiuse, then all clients will use same copy of
> running component. In case of singleuse design each user
> will have it's own copy of component. So you will have
> diffrenet behaviour, depending on design of ActiveX

> Val

> >-----Original Message-----
> >I have developed a 3 tiered , VB6,  Access 97 Db,
> application using
> >disconnected recordsets under ADO 2.1

> >When running the application in Windows 98 ,the DB
> component is an
> >ActiveX.exe which runs all the time.

> >In the initial test the first two tiers reside on the
> Work Stations

> >When the application starts up, a lot of  tables are read
> to load into the
> >Workstation.  Data that is used frequently is loaded into
> various Class
> >Modules and arrays

> >If two users start up their Work Stations at about the
> same time, we get an
> >Error 91: Object variable or with block variable not set

> >This happens when Vb tries to execute eg
> >    Set rs = Connect.Execute "Select......",  , adCmdText

> >I can see that I could use the Error Handler to pause
> and  execute the above
> >line until the DB is free.

> >Because Erro 91 can arise form other situations this
> approach does not
> >appeal.

> >Can anyone suggest where I might find some reference
> material on the
> >Conflict problem or suggest an alternative solution

> >Regards

> >Merv Couper

> >.



Sat, 04 Sep 2004 07:24:48 GMT  
 
 [ 3 post ] 

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