修改一个内存参数db_16k_cache_size,如下：

SQL> show parameter db_16k_cache_size

NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
db_16k_cache_size big integer 0
SQL> alter system set db_16k_cache_size=4M;

System altered.

SQL> show parameter db_16k_cache_size

NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
db_16k_cache_size big integer 96M
SQL> alter system set db_16k_cache_size=48M;

System altered.

SQL> show parameter db_16k_cache_size

NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
db_16k_cache_size big integer 96M
SQL> alter system set db_16k_cache_size=0;

System altered.

SQL> show parameter db_16k_cache_size

NAME TYPE VALUE
------------------------------------ ---------------------- ------------------------------
db_16k_cache_size big integer 0

可以看出,如果设置db_16k_cache_size的话,一次至少需要设置96M,否则无法成功.

关于db_16k_cache_size设置值的最小值,每次最少增加多大内存的系统信息,可以从视图V$SGA_DYNAMIC_COMPONENTS中看到.

如下,是在HP-UNIX上看到的,可以知道db_16k_cache_size每次至少增长4M.而每次的初始话最小值应该是跟主机有关系.
我试验的这台机器是在HP-UNIX上进行的,db_16k_cache_size的最小值是96M,而在Linux上测试最小值可以到10M.

SQL> select COMPONENT,CURRENT_SIZE,MIN_SIZE,LAST_OPER_MODE,LAST_OPER_TIME,GRANULE_SIZE from V$SGA_DYNAMIC_COMPONENTS;

COMPONENT CURRENT_SIZE MIN_SIZE LAST_OPER_MODE LAST_OPER_TI GRANULE_SIZE
------------------------------ ------------ ---------- -------------------- ------------ ------------
shared pool 83886080 83886080 4194304
large pool 4194304 4194304 4194304
java pool 4194304 4194304 4194304
streams pool 4194304 4194304 4194304
DEFAULT buffer cache 100663296 100663296 4194304
KEEP buffer cache 0 0 4194304
RECYCLE buffer cache 0 0 4194304
DEFAULT 2K buffer cache 0 0 4194304
DEFAULT 4K buffer cache 100663296 100663296 4194304
DEFAULT 8K buffer cache 0 0 4194304
DEFAULT 16K buffer cache 104857600 0 MANUAL 24-AUG-11 4194304

COMPONENT CURRENT_SIZE MIN_SIZE LAST_OPER_MODE LAST_OPER_TI GRANULE_SIZE
------------------------------ ------------ ---------- -------------------- ------------ ------------
DEFAULT 32K buffer cache 0 0 MANUAL 24-AUG-11 4194304
ASM Buffer Cache 0 0 4194304