Drop an Oracle database on Windows server

step 1: get datafile, control file and redo log file location

select file_name from dba_data_files
select name from v$controlfile
select member from v$logfile

step 2: set env variables if not done yet

set oracle_home=C:\Oracle\Orant1020
set oracle_sid=XXX

step 3: shutdown database and restart it in mount stage and restricted exclusively.

SQL> shutdown immediate;
SQL> startup mount exclusive restrict;

step 4: drop the DB and exit sqlplus

SQL> drop database;

step 5: check if the database files are removed, do it if not. Don't forget the folders, trc, alert file, etc.

step 6: Drop the XXX related services using ORADIM

C:\> oradim -delete -sid XXX
Instance deleted.

step 7: Check the listener if there is any XXX services and unregister them if yes. It does it by default, but in case.