ORA-01586: database must be mounted EXCLUSIVE and not open for this operation

ERROR

ORA-01586: database must be mounted EXCLUSIVE and not open for this operation

SOLUTION

$sqlplus / as sysdba

SQL>shutdown immediate;
Database closed.
Database dismounted.
ORACLE instance shut down.

SQL>startup mount exclusive restrict;
ORACLE instance started.

Total System Global Area 2112354232 bytes
Fixed Size                  2212208 bytes
Variable Size            1356068952 bytes
Database Buffers          838652800 bytes
Redo Buffers                4065272 bytes
Database mounted.

SQL>drop database;
Database dropped.