When you say "I made a system DSN in ODBC" do you mean a 64-bit system DSN or a 32-bit system DSN (System DSNs have bitness, unlike User DSNs)?

...or would it be more appropriate to tell User DSNs have a bitness, as well, but somehow magically they get synchronized between 32-bit and 64-bit? (AFAIK, they still appear under the according 32-bit/64-bit reg hives...)

Please set LogFile on the Advanced tab to a (unique) filename for each of the 32 bit working DSN and the 64 bit failing DSN and post the contents of the files generated after running a test connection. Also, please post the engine start line for the running engine on MachineA. It might be helpful if you were able to add -z (and -o <filespec> ) if not already on the server and post its contents also.

If you have concerns with posting those logs here, you can send them to me by email using this address: <lastname>@sybase.com

I think we're still confused as to what you're actually trying in your DSN settings. Both 64-bit and 32-bit ODBC drivers should be able to connect to a remote 64-bit (and 32-bit) database server. The fact that you see the error 'Unable to start database server' sounds like you may have a configuration issue in your DSN information (since this error appears when we have received client information to try to auto-start a local server, not connect to a remote server).

So I am unable to understand why 64-bit ODBC will not connect if I install Client version.

The client install has two versions included - the 32-bit and 64-bit components. Are you trying to just install the 32-bit components, perhaps?

You may find it helpful to dump the ODBC registry contents and compare them across machines to see if the ODBC driver is successfully installed/registered/configured the same in both cases (also see: http://www.sybase.com/detail?id=1091419 ):

regedit /e system_x64.reg HKEY_LOCAL_MACHINE\Software\ODBC
regedit /e system_x86.reg HKEY_LOCAL_MACHINE\Software\Wow6432Node\ODBC
regedit /e user_x64.reg HKEY_CURRENT_USER\Software\ODBC
regedit /e user_x86.reg HKEY_CURRENT_USER\Software\Wow6432Node\ODBC

Can you post the contents of the output from 'dbdsn' to see which DSNs are currently installed on the systems and how they're configured? (Being careful to remove database passwords?)

for /F "skip=2" %i in ('%SQLANY12%\bin32\dbdsn -lu') do "%SQLANY12%\bin32\dbdsn" -gu %i > sa_odbc_x86_user.txt
for /F "skip=2" %i in ('%SQLANY12%\bin32\dbdsn -ls') do "%SQLANY12%\bin32\dbdsn" -gs %i > sa_odbc_x86_system.txt
for /F "skip=2" %i in ('%SQLANY12%\bin64\dbdsn -lu') do "%SQLANY12%\bin64\dbdsn" -gu %i > sa_odbc_x64_user.txt
for /F "skip=2" %i in ('%SQLANY12%\bin64\dbdsn -ls') do "%SQLANY12%\bin64\dbdsn" -gs %i > sa_odbc_x64_system.txt

For System DSNs, the Windows registry has both 32-bit and 64-bit branches (they are in HKEY_LOCAL_MACHINE). Not so for User DSNs (they are in HKEY_CURRENT_USER).

Run these commands on the command line(where my-dsn is your DataSourceName and path-to-my-install is exactly that):

path-to-my-install\bin64\dbdsn -gs "my-dsn"

path-to-my-install\bin32\dbdsn -gs "my-dsn"

Do they show exactly the same settings?

Also, try the Test Connection buttons in the 64-bit and 32-bit ODBC Datasource Admins (odbcad32).

PS. I see that Jeff posted below an elegant way to dump your DSNs.

A correct configuration of ASA odbc DSN will not "try to start the database". Perhaps you have done a wrong config for the DSN.

Just give you a simple example: dbdsn.exe -y -ws aaa -c "Driver=SQL Anywhere 12;links=tcpip(host=machineB;port=5600;DoBroadCast=NONE;Verify=NO);dbn=ttt;"

will create a DSN connect to 5600 on machineB for the database name ttt. And the dsn name is "aaa".

If you are running 32bit dbdsn.exe, it will create a 32bit odbc DSN. Otherwise, it will create a 64bit odbc DSN.