Some common reasons that setup/connection issues occur are:
On Windows, UNIX, and Linux, the library path environment variable is not set correctly.
HP-UX ONLY:
When setting the library path environment variable on HP-UX operating systems, specifying the parent directory is not required.
You also must set the LD_PRELOAD environment variable to the fully qualified path of the libjvm.so[sl].
The library path environment variable is:
32-bit Drivers
PATH on Windows
LD_LIBRARY_PATH on Solaris, Linux and HP-UX Itanium
SHLIB_PATH on HP-UX PA_RISC
LIBPATH on AIX
64-bit Drivers
PATH on Windows
LD_LIBRARY_PATH on Solaris, HP-UX Itanium, and Linux
LIBPATH on AIX
The database and/or listener are not started.
The ODBCINI environment variable is not set correctly for the ODBC drivers on UNIX, Linux, or macOS.
The ODBC driver’s connection attributes are not set correctly in the system information file on UNIX, Linux, and macOS. See "Data Source Configuration on UNIX/Linux" or "Data Source Configuration for macOS" for more information. For example, the host name or port number are not correctly configured. See "Connection Option Descriptions" for a list of connection string attributes that are required for each driver to connect properly to the underlying database.
See "The Test Loading Tool" for information about a helpful diagnostic tool.
On Windows, UNIX, and Linux, the library path environment variable is not set correctly.