212.Note the following parameters settings in your database:
SGA_MAX_SIZE = 1024M
SGA_TARGET = 700M
DB_8K_CACHE_SIZE = 124M
LOG_BUFFER = 200M
You issued the following command to increase the value of DB_8K_CACHE_SIZE:
SQL> ALTER SYSTEM SET DB_8K_CACHE_SIZE=140M;
What would happen?
A. It will fail because DB_8K_CACHE_SIZE parameter cannot be changed dynamically
B. It will be successful only if the memory is available from the auto tuned components
C. It will fail because an increase in DB_8K_CACHE_SIZE cannot be accommodated within SGA_TARGET
D. It will fail because an increase in the DB_8K_CACHE_SIZE cannot be accommodated within SGA_MAX_SIZE
Answer: B

但标准答案是D

这道题说明数据库的标准块不是8K。如果是8K块，会报错。
SQL> alter system set db_8k_cache_size=100M scope=memory;
alter system set db_8k_cache_size=100M scope=memory
*
第 1 行出现错误:
ORA-02097: 无法修改参数, 因为指定的值无效
ORA-00380: 无法指定 db_8k_cache_size, 因为 8K 是标准块大小

数据调整缓冲区是SGA的组成部分：
 

SQL> show parameter sga

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

sga_max_size                         big integer 2432M

sga_target                           big integer 2432M

SQL> show parameter log_buff

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

log_buffer                           integer     19193856

SQL> show parameter 16k

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_16k_cache_size                    big integer 0

SQL> alter system set db_16k_cache_size=1000M ;

系统已更改。

SQL> show parameter sga

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

sga_max_size                         big integer 2432M

sga_target                           big integer 2432M

SQL> show parameter 16k

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_16k_cache_size                    big integer 1008M

SQL> ALTER SYSTEM SET db_cache_size=1000m;

系统已更改。

SQL> show parameter cache_size

NAME                                 TYPE        VALUE

------------------------------------ ----------- ------------------------------

db_16k_cache_size                    big integer 1008M

db_2k_cache_size                     big integer 0

db_32k_cache_size                    big integer 0

db_4k_cache_size                     big integer 0

db_8k_cache_size                     big integer 0

db_cache_size                        big integer 1008M

db_flash_cache_size                  big integer 0

db_keep_cache_size                   big integer 0

db_recycle_cache_size                big integer 0