Drop Database

Dropping a database sounds like an easy task this is why it's not well documented, but still it needs to be actioned properly.

In general, there are two ways of dropping a database, one is using dbca and the other through the RMAN.

As a matter of fact I don't trust GUI tools in my career which dbca is one of them, this is why I'll explain the manual method :-)
I'll explain the steps for dropping both standalone and a RAC database.

Before starting as a rule of thumb, take a backup of the database to be dropped and keep it on tape, just in case someone comes from nowhere asking you for the old data or for a pl/sql code.


Case1: Dropping a STANDALONE DB:

let's suppose the database name to be dropped is orcl.

First, if the database is already registered with Grid/Cloud Control un-register it:
Connect to Grid Control with an admin user (e.g. SYSMAN)
Targets -> Databases -> Select DB_NAME "ORCL" -> Remove

Restart the DB in "RESTRICT EXCLUSIVE" mode:

[By oracle]
# export ORACLE_SID=orcl
# sqlplus "/ as sysdba"
SQL> shu immediate;
SQL> startup mount exclusive restrict;
SQL> select INSTANCE_NAME,HOST_NAME from v$instance;

Drop the database from RMAN:
# export ORACLE_SID=orcl
# rman target /
Recovery Manager: Release 11.2.0.3.0 - Production on Wed Jan 10 10:19:48 2018

Copyright (c) 1982, 2011, Oracle and/or its affiliates.  All rights reserved.

connected to target database: ORCL (DBID=1220202490, not open)

RMAN> DROP DATABASE INCLUDING BACKUPS;
...
database name is "ORCL" and DBID is 1220202490
database dropped
RMAN> exit

Note:INCLUDING BACKUPS option will delete RMAN Backups/Datafiles & Controlfiles copies along with the Database files.

Remove the DB from ORACLE RESTART repository:
[By oracle]
# srvctl remove database -d orcl 

Delete the database entry from /etc/oratab: [both Nodes]

# vi /etc/oratab
[Remove the similar line]
orcl:/u01/app/oracle/product/11.2.0/dbhome_1:N
[Optional] Delete the instance files from $ORACLE_HOME/dbs:

# cd $ORACLE_HOME/dbs
# ls -l *orcl*

[Optional] Remove database diag directory from $ORACLE_BASE/diag/rdbms:

# adrci
ADR base = "/u01/app/oracle"

adrci> show homes rdbms
ADR Homes:
diag/rdbms/orcl/orcl

adrci> exit

# cd /u01/app/oracle/diag/rdbms
# rm -rf orcl