Instance Efficiencies 相关参数的解释

Instance Efficiencies 相关参数的解释
 
Library Hit%:shows the percentage of times a requested object was found in the cache.
             请求的对象在cache的次数占总请求数的百分比
Ideally this number is close to 100%.
             理想上这个值越大越好。

Soft Parse% shows the percentage of  times that a requested cursor was found and reused.
              请求的游标cursor被找到和重用的次数占总的请求数的百分比。
When this number is low, cursors are not being reused.
当这个值较小时，表明cursor没有被共享。

Execute to Parse%is the number of executions to  the number of parses.

This number could be negative if  executions have not occu rred before the end of a snap shot or if the shared
pool is too small and queries are aging out of the shared pool a nd need to be reparsed before they
have finished executing. When cursors are being shared th is number will approach 100%.

Parse CPU to Parse Elapsed%: the example shows that the CP U time is taking almost
none of the total elapsed time fo r parsing. The elapsed parse time  is likely being spent in waits.

Latch: shared pool indicates that there we re a large number of me mory allocations that
required holding the  shared pool latch.

Latch: row cache objectsindicates that there is conten tion loading, referencing, and
freeing objects in the data dictionary cache. This can be ca used by excessive row-cache access
operations in a hard-parse scenario.

Library Cache Activity 部分说明

two possible reasons for the reloads-to-pins ratio being greater than 1%:
? The shared parsed areas have been aged-out because of lack of space. This  can happen even
when the cursor is being used frequently.
Solution: Avoid the frequent reloads by increasing the  SHARED_POOL_SIZE
initialization parameter. For ma nual memory tuning, use the  Shared Pool Advisor to
determine the proper sizing of the shared pool.
? Shared parsed areas are invalidated.
Solution: Perform housekeeping (such as creating indexes and gathering  statistics) during
periods of light load.