-- set ORACLE env first

export ORACLE_SID=ORCL12
export ORACLE_HOME=/oracle/.....

oracle@oravm:~/ [ORCL12] rman target /

Recovery Manager: Release 12.1.0.1.0 - Production on Wed Dec 27 09:45:33 2017

Copyright (c) 1982, 2013, Oracle and/or its affiliates.  All rights reserved.

connected to target database (not started)

RMAN> startup force mount;

Oracle instance started
database mounted

Total System Global Area    4275781632 bytes

Fixed Size                     5218048 bytes
Variable Size               2415919360 bytes
Database Buffers            1845493760 bytes
Redo Buffers                   9150464 bytes

RMAN> show db_unique_name;

using target database control file instead of recovery catalog
RMAN configuration parameters for database with db_unique_name ORCL12 are:
RMAN configuration has no stored or default parameters

RMAN> SQL 'ALTER SYSTEM ENABLE RESTRICTED SESSION';

sql statement: ALTER SYSTEM ENABLE RESTRICTED SESSION

RMAN> DROP DATABASE INCLUDING BACKUPS NOPROMPT;

database name is "ORCL12" and DBID is 2242343723

allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=51 device type=DISK
specification does not match any backup in the repository

released channel: ORA_DISK_1
allocated channel: ORA_DISK_1
channel ORA_DISK_1: SID=51 device type=DISK
specification does not match any datafile copy in the repository
specification does not match any control file copy in the repository
specification does not match any control file copy in the repository
List of Archived Log Copies for database with db_unique_name ORCL12
=====================================================================

Key     Thrd Seq     S Low Time
------- ---- ------- - --------
1       1    1       A 30.11.17
        Name: +ORA_DATA/ORCL12/ARCHIVELOG/2017_11_30/thread_1_seq_1.407.961431639

2       1    2       A 30.11.17
        Name: +ORA_DATA/ORCL12/ARCHIVELOG/2017_11_30/thread_1_seq_2.414.961431685

3       1    3       A 30.11.17
        Name: +ORA_DATA/ORCL12/ARCHIVELOG/2017_12_01/thread_1_seq_3.316.961561207

deleted archived log
archived log file name=+ORA_DATA/ORCL12/ARCHIVELOG/2017_11_30/thread_1_seq_1.407.961431639 RECID=1 STAMP=961431639
deleted archived log
archived log file name=+ORA_DATA/ORCL12/ARCHIVELOG/2017_11_30/thread_1_seq_2.414.961431685 RECID=2 STAMP=961431684
deleted archived log
archived log file name=+ORA_DATA/ORCL12/ARCHIVELOG/2017_12_01/thread_1_seq_3.316.961561207 RECID=3 STAMP=961561206
Deleted 3 objects


database name is "ORCL12" and DBID is 2242343723
database dropped

RMAN>