error[ im014] [Microsoft][ODBC Driver Manager]The specified DSN contains an architecture mismatch between the Driver and Application
Some hint in the internet pointed out that I should use the 32 bit version of the ODBC admin console ODBCAD32.EXE.
So I entered the file name ODBCAD32.EXE into the windows menu's search field, and a link to a file named ODBCAD32.EXE was offered.
Unfortunately, there are two different executable files named ODBCAD32.EXE under 64 bit Windows 7. The one creating 64 bit data sources is %WINDIR%\System32\odbcad32.exe. I spite of all the 32's in the program's name and path, DSNs created by means of this executable do not work with 32 bit SQAPL.
The program version that creates 32 bit data sources is %WINDIR%\SysWow64\odbcad32.exe. DSNs created by means of this executable can be accessed from Dyalog 32 Bit Unicode SQAPL.