Start and Stop of oracle database on Linux

 connect to db using sqlplus

connect sys as sysdba

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


SQL> startup
ORACLE instance started.

Total System Global Area 1879048192 bytes
Fixed Size            2925696 bytes
Variable Size          637537152 bytes
Database Buffers     1224736768 bytes
Redo Buffers           13848576 bytes
Database mounted.
Database opened.
SQL>