-----------
java pool 4
large pool 4
shared pool 84
205.002403
205.002403=buffer cache + log buffer + fixed sga + all others ...
改动java pool的值
SQL> alter system set java_pool_size=20M;
SQL> select name, block_size, current_size,prev_size from v$buffer_pool;
name block_size current_size prev_size
----------------------------------------------------------------------------------------------
KEEP 8192 188 204
SQL> Select pool, sum(bytes)/1024/1024 as "M bytes" from v$SGASTAT
group by pool;
pool M bytes
-------------------------------------------------
java pool 20
large pool 4
shared pool 84
189.002403
可以看出, db_cache_size的值已经被自动调小了.
再把java pool 的值改回去
SQL> alter system set java_pool_size=8M;
SQL> select name, block_size, current_size,prev_size from v$buffer_pool;
name block_size current_size prev_size
-----------------------------------------------------------------------------------
KEEP 8192 188 204
SQL> select name, block_size, current_size,prev_size from v$buffer_pool;
pool M bytes
-------------------------------------------------
java pool 20
large pool 4
shared pool 84
189.002403
这一次, db_cache_size的值没有变化 , JAVA_POOL_SIZE的值也没有变化
修改large pool的值为16M
SQL> alter system set large_pool_size=16M;
System altered.
SQL> select name,block_size,current_size,prev_size from v$buffer_pool;
NAME BLOCK_SIZE CURRENT_SIZE PREV_SIZE
-------------------- ---------- ------------ ---------
DEFAULT 8192 176 188
SQL> Select pool, sum(bytes)/1024/1024 as "M bytes" from v$sgastat group by pool;
POOL M bytes
------------ ----------
java pool 20
large pool 16
shared pool 84
177.002403
这次，db_cache_size和large_pool_size的值都变了
同样,调大shared_pool_size后, db_cache_size会自动减小.
虽然db_nk_cache_size的值不会随着workload 的改变而自动调整, 我们还是可以看看手工改动db_nk_block_size 的情况
SQL> alter system set db_2k_cache_size=4m;
System altered.
SQL> select name,block_size,current_size,prev_size from v$buffer_pool;
NAME BLOCK_SIZE CURRENT_SIZE PREV_SIZE
---------------- ----------------- ------------ ----------
DEFAULT 8192 172 176
DEFAULT 2048 4 0 <