Dbca cannot identify an existing database

Dbca cannot identify an existing database

When you delete an unnecessary test database at the customer's site and use dbca, the database cannot be found. It's strange that it's starting !!

Later, I searched for oratab in the operating system and obtained the file to/etc to identify it. But why didn't I find the file in/etc?

When creating a database, select both the database software and database creation (sid: orcl2 ):

Dbca:

Simulated. When creating a database in the future, it is best to separate the database software from the database.