Solution for [DBT-10317] Specified SID Name (SID) already exists when running dbca

When running dbca, for example like this:

dbca -createDatabase -responsefile ./cdb.rsp -silent
[FATAL] [DBT-10317] Specified SID Name (cdb) already exists.
   ACTION: Specify a different SID Name that does not already exist.

There are two potential reasons for the error:

1. you have a /etc/oratab which has an entry, for example:

cdb:/installedsw1/oracle/product/Ora19c:Y

2. your instance is running.

Solution to case 1: remove entry

Solution to case 2: shutdown the instance

Rerun dbca and it will now proceed as expected.