IF UI is not available then how can we create a database in Oracle?

Using the CREATE DATBASE SQL statement is a more manual approach to creating a database. If you use the CREATE DATABASE statement, you must complete additional actions before you have an operational database. These actions include building views on the data dictionary tables and installing standard PL/SQL packages. You perform these actions by running prepared scripts.

If you have existing scripts for creating your database, consider editing those scripts to take advantage of new Oracle Database features.

The instructions are for single-instance installations only. Refer to the Oracle Real Application Clusters (Oracle RAC) installation guide for creating an Oracle RAC database.

Complete the following steps to create a database with the CREATE DATABASE statement.

Step1: Specify an Instance Identifier (SID)

Step2: Ensure That the Required Environment Variables Are Set

Step3: Choose a Database Administrator Authentication Method

Step4: Create the Initialization Parameter File

Step5: (Windows Only) Create an Instance

Step6: Connect to the Instance

Step7: Create a Server Parameter File

Step8: Start the Instance

Step9: Issue the CREATE DATABASE Statement

Step10: Create Additional Tablespaces

Step11: Run Scripts to Build Data Dictionary Views

Step12: Run Scripts to Install Additional Options (Optional)

Step13: Back Up the Database.

Step14: (Optional) Enable Automatic Instance Startup

For More Detail on this kindly visit the following link :

https://docs.oracle.com/cd/B19306_01/server.102/b14231/create.htm

There are three methods for creating a database i.e. Manually,DBCA,and OMF. apart of these any other method any body know to create a database.