Oracle Drop database

To drop a database I did the following :

SQL> shutdown abort;
startup mount exclusive restrict;
ORACLE instance shut down.
SQL> ORACLE instance started.

Total System Global Area 630501376 bytes
Fixed Size 2147032 bytes
Variable Size 469765416 bytes
Database Buffers 150994944 bytes
Redo Buffers 7593984 bytes
Database mounted.
SQL> connect as sysdba
Enter password:
Connected.
SQL> drop database;

Change Oracle default port

Change the port in
listener.ora
tnsnames.ora

eg.,
LISTENERS_OARCLE1=
(DESCRIPTION =
(ADDRESS = (PROTOCOL = TCP)(HOST = oracle1)(PORT = 5599)(IP = x.x.x.x))
)