By default, AQT is installed as a 32-bit application. When you install AQT on a 64-bit machine, a 64-bit version of AQT will also be installed - you will have icons on your desktop for both the 32-bit and 64-bit versions of AQT.
On a Windows 64-bit machine you have the choice of running either the 32-bit or 64-bit version of AQT. Which one you will use will depend on the the ODBC Datasource you are wishing to connect to:
AQT v8 (and earlier versions of AQT) run OK on a 64-bit version of Windows. These versions of AQT are 32-bit applications only, so will not be able to access a 64-bit ODBC Driver.
The 32-bit and 64-bit AQT executables are the same program and have identical capabilities (they have just been compiled with different settings). Their performance is almost identical, though the 32-bit edition may be slightly faster on machines which are memory constrained.
The 64-bit executable uses more memory than the 32-bit executable. This is because all memory-address pointers use 64-bits rather than 32-bits.
The only advantage of the 64-bit AQT is that it can use more memory. 32-bit applications are unable to use more than 2 GB of memory. In most cases AQT uses far less memory than this. However if you have a lot of physical memory on your machine, and you wish to display very large tables, the 2GB memory limit of the 32-bit AQT may be a limitation for you. In this case, running the 64-bit AQT will allow you to display a larger amount of data.
On the Signon window you will be shown a list of datasources. On a 64-bit machine this can be confusing, as this list can contain some datasources you will be unable to connect to. In addition some of your ODBC Datasources may not appear in this list.
This list contains:
You may not be able to connect to all the User Datasources as some of these may be incompatible with the version of AQT you are running.
Note that you cannot tell from this list which are System and which are User Datasources, nor can you tell which are 32-bit or 64-bit datasources.
If you attempt to connect to connect to a datasource that uses an incompatible ODBC driver, you will get the message:
Data source name not found and no default driver specified
The specified DSN contains an architectural mismatch between the Driver and Application
The solution is to connect to this datasource using the appropriate version of AQT (32-bit or 64-bit).
This is described in more detail in http://support.microsoft.com/kb/942976
You can add new datasources with the New button or ODBC Admin > Add. In both these cases you will only see the Drivers which are appropriate for that architecture of Windows. In other words, adding datasources in this way works well.
Configuring existing datasources runs into the same problem as mentioned in the previous section. The list of datasources may contain datasources which are not valid for that version of Windows. Clicking on Configure or ODBC Admin > Configure can give you the message:
The setup routines for xxxx ODBC Driver cannot be found
The solution here is to use the appropriate version of AQT for that datasource.
When you attempt to connect to an Oracle database, you may get the message:
TNS could not resolve the connect identifier
There are a number of possible causes of this error message - see Oracle - Diagnosing Connection Problems. However, there is a problem in the 64-bit Windows environment that may be responsible for this problem. This is discussed below.
By default, AQT will be installed into C:\Program Files (x86)\Advanced Query Tool. The Program Files (x86) directory structure is used for 32-bit applications. However there is a bug in the Oracle client - when you run a program which has a bracket in the path, the Oracle client will fail to parse tnsnames.ora correctly, resulting in the above message.
The resolution to this problem is to install AQT into a directory that doesn't have a bracket in the name.
This problem has been fixed in recent versions of the Oracle Client.