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   ► MB LobbyPascal and Delphi Coding BoardDelphi Single User Apps Topic   Print This     

'Access violation at address...' error

'Access violation at address...' error in Delphi Single User Apps topic (part of our Pascal and Delphi Coding group).

Quick Search: 'Access   violation   address   'Access violation   'Access violation at   address '  
Shyami
 (Inactive)
Ireland
Hello pals,

I have a Delphi application connecting to an Oracle database sitting on a Citrix server. When I try to do certain things I get an error 'Access violation at address...' The application was not developed inhouse and I do not know Delphi & Citrix so I can't guess why I get the error message. I get this message even when I am logged in as administrator on the citrix server and try to open a client session from there. The application runs without any problem on Windows NT/98. The problem seems to be specific to Citrix and Delphi, can anybody please help.

Hope I have given enough details.

Thanks,
Confused
-Shyami
 Posted 17 years ago (Thread Starter)
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Post ID #6359, 5 replies
Thread Started 5/29/2002 2:03:00 AM
View Counter=17343
Last Reply Posted 6/4/2002 3:05:00 AM)
Location=Ireland  
Joined=17 years ago   MB Posts=3  
Shyami
 (Inactive)
Ireland
Hi Scott,

Thanks for the response!

I checked all that you said and everything seems to be ok. I can connect to Oracle using SQL*Plus. Even using the application, I can proceed to a certain extent before I get the error, so it does connect to the database properly, retrieves the data and then when I try using some functions I have this problem, the functions are ok when I use it on my pc as a single user application, only when I put it on citrix I have a problem so I do not know if it is Citrix or Delphi.

Thanks again,
-Shyami
 Posted 17 years ago (Thread Starter)
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Post ID #6389 (Level 1.1)  Reply to 6359
Thread Started 5/31/2002 2:28:00 AM
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Location=Ireland  
Joined=17 years ago   MB Posts=3  
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Shyami
 (Inactive)
Ireland
Thanks for the reply Scott, I will try to check out the permissions on the directories. I will let you know if my application worked and how, hopefully it should help someone who is having the same problems as me!

Thanks again,
-Shyami
 Posted 17 years ago (Thread Starter)
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Post ID #6471 (Level 1.2)  Reply to 6359
Reply Posted 6/4/2002 3:05:00 AM
Location=Ireland  
Joined=17 years ago   MB Posts=3  
Scott Wehrly
Prestwood IT
 (Inactive)
Las Vegas, NV USA
Well, "Access violation at address" is to generic to pin down the exact error, but most of the time, Delphi reports this when an object is no longer valid, or there is a memory access violation.




That doesn't make this error clear, but if Delphi is trying to open a table where there isn't a connection to the database, it can cause the "Access violation" error.




We're using a Delphi app connected to a SQL Server database on Citrix. I would try checking your client connectivity to Oracle from the Citrix session. The simplest way to do this is to start a SQLPlus session, or run one of the other applications that comes with an Oracle Client installation (in other words, rule out the Delphi app).




If that isn't the problem, check which database user Oracle thinks you are. Once you connect to the database in SQLPlus, type "show user". If the Userid isn't the correct Userid for the Delphi application, then someone must have set up your Oracle client incorrectly on the Citrix workstation. You could have a session-mapped UID in effect for Oracle, in which case the Delphi app probably won't log in to the database correctly.
 Posted 17 years ago
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Post ID #6382 (Level 1.3)  Reply to 6359
Reply Posted 5/30/2002 2:04:00 PM
Location=Las Vegas, NV USA 
Joined=17 years ago   MB Posts=442   KB Posts=19  
Scott Wehrly
Prestwood IT
 (Inactive)
Las Vegas, NV USA
Well, you've provided some more useful information, and it doesn't appear to be a connection issue with Oracle.



But you do say that it's happening with some of the functions in the Delphi application. The fact that they work on your workstation, but not on Citrix, might also be a permissions problem with disk files or directories. If the Delphi app is trying to create a temporary directory, or add files to a folder that your Citrix user doesn't have authorization to write, that could also cause the "Access violation".



It's too bad that the app wasn't done in house, because you could debug the code to find what's causing the error. It's apparent that the code was not written well, with exception handlers that give you a useful message to go along with the error - expected practice whenever dealing with external resources creation in Delphi.
 Posted 17 years ago
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Post ID #6411 (Level 1.4)  Reply to 6359
Reply Posted 5/31/2002 1:08:00 PM
Location=Las Vegas, NV USA 
Joined=17 years ago   MB Posts=442   KB Posts=19  
Scott Wehrly
Prestwood IT
 (Inactive)
Las Vegas, NV USA
Oops!



I just noticed - you said you were logged in as the Citrix administrator. That would rule out the permissions issue.



But, it could be a related problem. I've had experience with Citrix sessions that can't see a particular mapped network drive - even though every workstation on the network can see it.



This doesn't look easy to pin down. It's most likely some kind of system resource that the Delphi app is trying to access, that a Windows workstation user can access, but the Citrix user can't.



If this doesn't help, you may need to have the developers of the app take a look at it. If they're no longer available, you may need to farm it out for a code review by a certified developer.
 Posted 17 years ago
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Post ID #6414 (Level 1.5)  Reply to 6359
Reply Posted 5/31/2002 1:18:00 PM
Location=Las Vegas, NV USA 
Joined=17 years ago   MB Posts=442   KB Posts=19  

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