先來看一個“看起來”比較奇怪的現象
SQL> col name for a40
SQL> col value for a30
SQL> select name,value
2 from v$parameter
3 where name in
4 ('large_pool_size','java_pool_size','shared_pool_size','streams_pool_size',
'db_cache_size');
NAME VALUE
---------------------------------------- ------------------------------
shared_pool_size 0
large_pool_size 0
java_pool_size 0
streams_pool_size 0
db_cache_size 0
怎麼回事，怎麼會都是0呢？上REFERENCES查一下db_cache_size這個參數，其中有一句話如下：
If SGA_TARGET is set: If the parameter is not specified, then the default is 0 (internally determined by the Oracle Database). If the parameter is specified, then the user-specified value indicates a minimum value for the memory pool.
這下就很清楚了吧，因為使用了10G ASSM自動共享記憶體管理。
那麼如何檢視系統在某個時刻這些參數到底被自動的調整到了什麼值呢？
SQL> select x.ksppinm name,y.ksppstvl value,x.ksppdesc describ
2 from sys.x$ksppi x,sys.x$ksppcv y
3 where x.inst_id=userenv('Instance')
4 and y.inst_id=userenv('Instance')
5 and x.indx=y.indx
6 and x.ksppinm like '%pool_size%'
7 /
NAME VALUE DESCRIB
-------------------- ---------- ----------------------------------------
_NUMA_pool_size Not specif aggregate size in bytes of NUMA pool
ied
__shared_pool_size 79691776 Actual size in bytes of shared pool
shared_pool_size 0 size in bytes of shared pool
__large_pool_size 4194304 Actual size in bytes of large pool
large_pool_size 0 size in bytes of large pool
__java_pool_size 4194304 Actual size in bytes of java pool
java_pool_size 0 size in bytes of java pool
__streams_pool_size 0 Actual size in bytes of streams pool
streams_pool_size 0 size in bytes of the streams pool
NAME VALUE DESCRIB
-------------------- ---------- ----------------------------------------
_io_shared_pool_size 4194304 Size of I/O buffer pool from SGA
_backup_io_pool_size 1048576 memory to reserve from the large pool
global_context_pool_ Global Application Context Pool Size in
size Bytes
olap_page_pool_size 0 size of the olap page pool in bytes
13 rows selected.
SQL> edit
Wrote file afiedt.buf
1 select x.ksppinm name,y.ksppstvl value,x.ksppdesc describ
2 from sys.x$ksppi x,sys.x$ksppcv y
3 where x.inst_id=userenv('Instance')
4 and y.inst_id=userenv('Instance')
5 and x.indx=y.indx
6* and x.ksppinm like '%db_cache_size%'
SQL> /
NAME VALUE DESCRIB
-------------------- ---------- ----------------------------------------
__db_cache_size 83886080 Actual size of DEFAULT buffer pool for s
tandard block size buffers
db_cache_size 0 Size of DEFAULT buffer pool for standard
block size buffers
從上面結果中黑體部分可以看到，這些由兩個下劃線開頭的參數決定了目前SGA的配置設定，也是動态記憶體管理調整的參數。這些參數的更改會被記錄到SPFILE檔案中，在下一次資料庫啟動時仍然有效。
通過ORACLE 10G新增加的動态視圖v$sga_dynamic_components，可以看各個動态元件調整的時間和調整類型等資訊。
SQL> select component,current_size,min_size,last_oper_type,
2 last_oper_mode,to_char(last_oper_time,'yyyy-mm-dd hh24:mi:ss') LOT
3 from v$sga_dynamic_components
4 /
COMPONENT CURRENT_SIZE MIN_SIZE LAST_OPER_TYP LAST_OPER LOT
-------------------- ------------ ---------- ------------- --------- -----------
--------
shared pool 79691776 75497472 GROW IMMEDIATE 2009-11-25
20:11:08
large pool 4194304 4194304 STATIC
java pool 4194304 4194304 STATIC
streams pool 0 0 STATIC
DEFAULT buffer cache 83886080 83886080 SHRINK IMMEDIATE 2009-11-25
20:11:08
KEEP buffer cache 0 0 STATIC
RECYCLE buffer cache 0 0 STATIC
DEFAULT 2K buffer ca 0 0 STATIC
che
DEFAULT 4K buffer ca 0 0 STATIC
COMPONENT CURRENT_SIZE MIN_SIZE LAST_OPER_TYP LAST_OPER LOT
-------------------- ------------ ---------- ------------- --------- -----------
--------
che
DEFAULT 8K buffer ca 0 0 STATIC
che
DEFAULT 16K buffer c 0 0 STATIC
ache
DEFAULT 32K buffer c 0 0 STATIC
ache
COMPONENT CURRENT_SIZE MIN_SIZE LAST_OPER_TYP LAST_OPER LOT
-------------------- ------------ ---------- ------------- --------- -----------
--------
ASM Buffer Cache 0 0 STATIC
13 rows selected.