sqlplus system/manager@LEGACYDB
He tried the 64-bit version by accident. Installed it. Configured TNS_ADMIN . Tested: 32 bit oracle client download
sqlplus user/pass@olddb Error: The application was unable to start correctly (0xc000007b). That error code meant one thing: . His Python (32-bit) was talking to Oracle (64-bit) via a broken bridge. 32 bit oracle client download
Unzipped. Set PATH . Set TNS_ADMIN . Copied a working tnsnames.ora . 32 bit oracle client download