1.connection to server failed, probable Oracle Net admin error
The solution is to replace the Oci.dll file in your Navicat installation directory with the Oci.dll file (which you can find by searching) under your current Oracle installation path.
2.cannot load OCI dll,193 ...
The solution is: here http://www.oracle.com/technetwork/cn/topics/winsoft-095945-zhs.html download the corresponding Oracle version, The Oracle version I need to connect to is the first version of 11g, click I agree, download two jar pack in red circle
First unpack the package separately, and then copy all the contents of the Sqlplus into the basic package.
The picture in the circle is copied from the Sqlplus package.
Open navicat-> Tools, options, other->oci
Choose
Click OK, close Navicat, open again, you can connect.
There was a problem linking Oracle with Navicate