[oracle@bi11g bin]$ ./sqlplus /nolog
SQL*Plus: Release 11.2.0.1.0 Production on Fri Dec 1618:39:36 2011
Copyright (c) 1982, 2009, Oracle. All rights reserved.
SQL> conn / as sysdba
Connected.
SQL> show parameter memory
NAME TYPE VALUE
------------------------------------ -----------------------------------------
hi_shared_memory_address integer 0
memory_max_target big integer 1584M
memory_target big integer 1584M
shared_memory_address integer 0
SQL> alter system set memory_target = 512M scope=spfile
2 ;
System altered.
SQL> alter system set memory_max_target =1024Mscope=spfile
2 ;
System altered.
SQL> show parameter memory
NAME TYPE VALUE
------------------------------------ -----------------------------------------
hi_shared_memory_address integer 0
memory_max_target big integer 1584M
memory_target big integer 1584M
shared_memory_address integer 0
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 1068937216 bytes
Fixed Size 2220200 bytes
Variable Size 859836248 bytes
Database Buffers 201326592 bytes
Redo Buffers 5554176 bytes
Database mounted.
Database opened.
SQL> show parameter memory
NAME TYPE VALUE
------------------------------------ -----------------------------------------
hi_shared_memory_address integer 0
memory_max_target big integer 1G
memory_target big integer 512M
shared_memory_address integer 0
SQL>