Oracle 视图 DBA_HIST_LIBRARYCACHE 官方解释，作用，如何使用详细说明
本站中文解释
DBA_HIST_LIBRARYCACHE是Oracle提供的一个视图，可以用来查看缓存中对象的访问次数和命中次数，以及对应的命中率等表现数据。DBA_HIST_LIBRARYCACHE视图有利于用户了解某个对象是如何被访问和命中的，是否需要改善该对象的缓存状态，是否合理分配资源，以便追求最优的性能。
使用DBA_HIST_LIBRARYCACHE的步骤如下：
1.查询视图：使用select * from dba_hist_librarycache;查询出视图中的内容；
2.从查询结果中查询对应对象在缓存中的命中率：使用select name, gethitratio, pinhitratio, reloads from dba_hist_librarycache where name=’对象名’;查询出每个对象的命中率；
3.通过命中率了解对象的访问状况：如果命中率过低，则可以考虑重新调整内存的分配方式来优化缓存的命中率；
4.对不必要的对象加以缓存：可以在缓存中检查是否存在不必要的对象，如果有，则可以将不必要的对象从缓存中移除；
5.优化系统性能：根据缓存中的数据，系统管理员可以找出影响性能的潜在因素，从而找出改善性能优化系统性能的有效方案。
官方英文解释
DBA_HIST_LIBRARYCACHE displays historical statistics about library cache performance and activity.
This view contains snapshots of V$LIBRARYCACHE.
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Unique snapshot ID |
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Database ID for the snapshot |
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Instance number for the snapshot |
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Library cache namespace |
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Number of times a lock was requested for objects of the namespace |
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Number of times an object’s handle was found in memory |
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Number of times a PIN was requested for objects of the namespace |
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Number of times all of the metadata pieces of the library object were found in memory |
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Any PIN of an object that is not the first PIN performed since the object handle was created, and which requires loading the object from disk |
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Total number of times objects in the namespace were marked invalid because a dependent object was modified |
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Number of GET requests lock instance locks |
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Number of PIN requests lock instance locks |
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Number of release requests PIN instance locks |
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Number of GET requests for invalidation instance locks |
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Number of invalidation pings received from other instances |
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The database ID of the PDB for the sampled session |
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The ID of the container that
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See Also:
“V$LIBRARYCACHE”
