Mysql – Oracle database link to MySQL database on RedHat Linux

One of the key differences between these platforms is that a database in MySQL is a schema in Oracle. Since a schema in Oracle is also a user, the command you are looking for is CREATE USER. I highly recommend that you read the Oracle Concepts Guide before continuing. You may also find this documentation on MySQL>>Oracle migrations using SQL Developer useful. Here is the part relevant to your situation:

When migrating MySQL databases to Oracle, SQL Developer maps each MySQL database to a tablespace in Oracle. Database objects, such as tables, indexes and views are stored in the respective tablespaces and are referenced from the Oracle schema for the user that owns them.

From the error message perspective, the salient part to pull out is "ORA-01100: database already mounted". This indicates that a database has already been created and mounted. It may also be open. Here is an example reproducing your issue, opening the database (which may not be necessary if it is already open) and creating a django user.

SQL> create database django;
create database django
*
ERROR at line 1:
ORA-01501: CREATE DATABASE failed
ORA-01100: database already mounted


SQL> SELECT status FROM v$instance;

STATUS
------------
MOUNTED

SQL> ALTER DATABASE OPEN;

Database altered.

SQL> SELECT status FROM v$instance;

STATUS
------------
OPEN

SQL> create database django;
create database django
*
ERROR at line 1:
ORA-01501: CREATE DATABASE failed
ORA-01100: database already mounted


SQL> CREATE USER django IDENTIFIED BY "No More ORA-001100.";

User created.

You should also assign permissions and create a django tablespace setting it as the default tablespace for django.

Metalink 207303.1 is the Client/ Server Interoperability Matrix which will be the definitive documentation. Since the express edition of 10g is based on Oracle 10.2, a database link to an 8.1.7 database should be supported. Database links to earlier versions of 8i (8.1.5 or 8.1.6) are not supported from a 10.2 database. For general sanity, I'd strongly suggest that the 8i side be running at least the 8.1.7.4 patchset but that isn't strictly required.