Instance Efficiencies 相关参数的解释
2013-05-06 22:30
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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.
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.
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