In fact, Navicat cannot connect to the ORACLE database because of the problem of the oci.dll file. The solution is to find the oci.dll file in the Oracle installation path and replace the oci.dll file in the Navicat installation path.
The oci.dll file path in the ORACLE database installation path is:
\app\ACER\product\11.2.0\dbhome_1\BIN\oci.dll
The oci.dll file path in the Navicat installation path is:
\Navicat Premium\instantclient_10_2\oci.dll