ORA-01034: ORACLE not available & ORA-00838: Specified value of MEMORY_TARG

bash-4.1$ ./sqlplus /nolog

SQL*Plus: Release 12.1.0.1.0 Production on Sat Nov  02 18:53:58 2013

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

SQL> conn / as sysdba

Connected.

SQL> alter system set sga_target=2G scope=SPFILE;

System altered.

SQL> ALTER SYSTEM SET session_cached_cursors=200 scope=spfile;

System altered.

SQL> alter system set processes=300 scope=spfile;

System altered.

SQL> alter system set shared_pool_size=600m scope=spfile;

System altered.

SQL> alter system set pga_aggregate_target=1g scope=spfile;

System altered.

SQL> alter system set open_cursors=300 scope=spfile;

System altered.

SQL> shutdown immediate;

Database closed.

Database dismounted.

ORACLE instance shut down.

SQL> startup

ORA-00838: Specified value of MEMORY_TARGET is too small, needs to be at least 3072M

SQL> create pfile from spfile;

File created.

Change the value of MEMORY_TARGET parameter.

$ vi /ora/oracle/dbs/initcdb1.ora

MEMORY_TARGET=0

bash-4.1$ ./sqlplus /nolog

SQL*Plus: Release 12.1.0.1.0 Production on Sat Nov  02 19:53:58 2013

Copyright (c) 1982, 2013, Oracle.  All rights reserved.

SQL> conn / as sysdba
Connected to an idle instance.
SQL> startup pfile='/ora/oracle/dbs/initcdb1.ora';
ORACLE instance started.

Total System Global Area 2137886720 bytes
Fixed Size    2290416 bytes
Variable Size  805309712 bytes
Database Buffers 1325400064 bytes
Redo Buffers    4886528 bytes
Database mounted.
Database opened.