sga_max_size：SGA允许的最大值，修改必须重启； sga_target：必须小于sga_max_size, 表示当前SGA的最大值； alter system set shared_pool_size=xxM scope=both;
3. 使用V$SHARED_POOL_ADVICE来设置shared pool的大小
V$SHARED_POOL_ADVICE displays information about estimated parse time in the shared pool for different pool sizes. The sizes range from 10% of the current shared pool size or the amount of pinned library cache memory (whichever is higher) to 200% of the current shared pool size, in equal intervals. The value of the interval depends on the current size of the shared pool.
| Column | Datatype | Description |
|---|---|---|
| SHARED_POOL_SIZE_FOR_ESTIMATE | NUMBER | Shared pool size for the estimate (in megabytes) |
| SHARED_POOL_SIZE_FACTOR | NUMBER | Size factor with respect to the current shared pool size |
| ESTD_LC_SIZE | NUMBER | Estimated memory in use by the library cache (in megabytes) |
| ESTD_LC_MEMORY_OBJECTS | NUMBER | Estimated number of library cache memory objects in the shared pool of the specified size |
| ESTD_LC_TIME_SAVED | NUMBER | Estimated elapsed parse time saved (in seconds), owing to library cache memory objects being found in a shared pool of the specified size. This is the time that would have been spent in reloading the required objects in the shared pool had they been aged out due to insufficient amount of available free memory. |
| ESTD_LC_TIME_SAVED_FACTOR | NUMBER | Estimated parse time saved factor with respect to the current shared pool size |
| ESTD_LC_LOAD_TIME | NUMBER | Estimated elapsed time (in seconds) for parsing in a shared pool of the specified size |
| ESTD_LC_LOAD_TIME_FACTOR | NUMBER | Estimated load time factor with respect to the current shared pool size |
| ESTD_LC_MEMORY_OBJECT_HITS | NUMBER | Estimated number of times a library cache memory object was found in a shared pool of the specified size |
可以使用下面的SQL语句来预估shared pool的大小： select 'Shared Pool' component,shared_pool_size_for_estimate estd_sp_size,estd_lc_time_saved_factor parse_time_factor,case when current_parse_time_elapsed_s + adjustment_s<0 then 0 else current_parse_time_elapsed_s + adjustment_s end response_time from ( select shared_pool_size_for_estimate,shared_pool_size_factor,estd_lc_time_saved_factor,a.estd_lc_time_saved,e.value/100 current_parse_time_elapsed_s,c.estd_lc_time_saved - a.estd_lc_time_saved adjustment_s from v$shared_pool_advice a, (select * from v$sysstat where name='parse time elapsed') e, (select estd_lc_time_saved from v$shared_pool_advice where shared_pool_size_factor=1) c ); COMPONENT ESTD_SP_SIZE PARSE_TIME_FACTOR RESPONSE_TIME -------------- ----------------- ------------------------- ------------- Shared Pool 64 .9989 294.37 Shared Pool 72 1 257.37 Shared Pool 80 1.0009 226.37 Shared Pool 88 1.0016 201.37 Shared Pool 96 1.0022 181.37 Shared Pool 104 1.0027 166.37 Shared Pool 112 1.0029 156.37 Shared Pool 120 1.0032 149.37 Shared Pool 128 1.0033 144.37 Shared Pool 136 1.0034 141.37 Shared Pool 144 1.0034 139.37