_ksmg_granule_size oracle内存分配粒度
_ksmg_granule_size:
内存分配粒度大小
oracle内存分配的最小单位，最终分配的内存数量都是这个参
数的整数倍
10g中这个参数的大小一般遵循如下原则：
– sga_max_size < = 1024M then _ksmg_granule_size = 4M
- sga_max_size > 1024M then _ksmg_granule_size = 16M
SQL> show parameter sga
NAME TYPE VALUE
------------------------------------ ----------- -----
-------------------------
sga_max_size big integer 164M
sga_target big integer 0
SQL> select x.ksppinm name,y.ksppstvl value,x.ksppdesc
descbtion
2 from x$ksppi x,x$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 '%_ksmg_granule%';
rows will be truncated
NAME VALUE
-------------------------------- ---------------------
-----
_ksmg_granule_size 4194304
SQL> show parameter sga
NAME TYPE VALUE
------------------------------------ ----------- -----
-------------------------
lock_sga boolean FALSE
pre_page_sga boolean FALSE
sga_max_size big integer 18000M
sga_target big integer 18000M
SQL> select x.ksppinm name,y.ksppstvl value,x.ksppdesc
descbtion
2 from x$ksppi x,x$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 '%_ksmg_granule%';
NAME VALUE
------------------------------
_ksmg_granule_size 16777216
----------------------------------
这个参数调整并不是任意的，还受到sga总量的限制，如果sga
不够，即使调整参数也不会生效，只能调整到系统能够认到的
最大值
SQL> alter system set "_ksmg_granule_size"=16777216
scope=spfile;
System altered.
SQL>
SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORACLE instance started.
Total System Global Area 176160768 bytes
Fixed Size 787588 bytes
Variable Size 149683068 bytes
Database Buffers 25165824 bytes
Redo Buffers 524288 bytes
Database mounted.
Database opened.
SQL> select x.ksppinm name,y.ksppstvl value,x.ksppdesc
descbtion
2 from x$ksppi x,x$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 '%_ksmg_granule%';
rows will be truncated
NAME
VALUE
------------------------------------------------------
-------------------------- --------------------------
_ksmg_granule_size
8388608
因为本地内存太小，并没有调整到16m，而是8m
)