大家好，又见面了，我是你们的朋友全栈君。
SGA_MAX_SIZE: static parameter
To use ASMM，need two parameters:
1.SGA_TARGET not null or zero;
2.STATISTICS_LEVEL = TYPICAL ( or ALL)
when u use ASMM,the sga is auto management
example:
SGA_MAX_SIZE : 12G
SGA_TARGET : 10G
2G (12G-10G) memory is not use at all.
parameters:
LOG_BUFFER=1G;( the parameter is only for the example and assume there is no fixed sga ,actually it is impossible)
other parameters = 0
steps:
1.
ALTER SYSTEM SET DB_CACHE_SIZE=8G； — succeed!
2.
ALTER SYSTEM SET DB_CACHE_SIZE=2G; — succeed!
3.
ALTER SYSTEM SET SHARED_POOL_SIZE=6G; — succeed!
4.
ALTER SYSTEM SET SHARED_POOL_SIZE=1G; — succeed!
5.
ALTER SYSTEM SET DB_CACHE_SIZE=4G; — failed !
SHOW PARAMETER SHARED_POOL_SIZE
it will display: 1G
u can not manually set the DB_CACHE_SIZE to 4G，unless u disable the ASMM.
—————————————
SHARED_POOL_SIZE,
LARGE_POOL_SIZE,
JAVA_POOL_SIZE,
STREAMS_POOL_SIZE
will the same result.
—————————————
DB_KEEP_CACHE_SIZE,
DB_RECYCLE_CACHE_SIZE,
nK BLOCK CACHE SIZE
are not the same result.
If u use DB_KEEP_CACHE_SIZE replaces SHARED_POOL_SIZE,
step 5 will succeed!
—————————————
doc says:
DB_KEEP_CACHE_SIZE is manual component ,so when it shrink,the auto components can use the memory immediate.
but:
DB_CACHE_SIZE is auto too! when shrink this parameter,query v$sgainfo and
v$sga_dynamic_comonents ,it size does not change, but the memory can be used immediate.
see : step 1,2,3
so i guess parameter “cache” is different from “pool”.
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转载于:http://blog.itpub.net/12807983/viewspace-695771/
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