关于Oracle 12c 中的Heat Map

最新推荐文章于 2023-03-27 18:14:08 发布

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#Oracle #Heat Map #Heat_Map

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HeatMap是Oracle Database 12c的一项特性，它可以收集系统生成的数据使用统计信息，包括行级和段级的信息。这些信息可用于自动化压缩和移动数据，从而降低存储成本、提高性能并优化数据库存储。HeatMap可以跟踪表和分区的最后修改及访问时间，并显示行级的修改时间。通过启用HeatMap，系统会自动收集段级和行级的统计数据，用于定义将自动维护的数据压缩和存储策略。

关于Oracle 12c 中的Heat Map:
以下摘自：Information Lifecycle Management (ILM), Heat Map, Automatic Data Optimization (ADO) (文档 ID 1612385.1)

Heat Map is an Oracle Database 12c feature that stores system-generated data usage statistics at the row and segment levels – information that can be used to automate the compression and movement of data in order to reduce storage costs, improve performance and optimize Oracle Database storage. Heat Map, used in conjunction with Automatic Data Optimization can automate compression and storage policies based on the usage of the data. Segment level Heat Map tracks the time of last modification and access of tables and partitions. Row level Heat Map shows modification times at the row level. Heat Map, once enabled, automatically collects segment and row level statistics that can be used to define compression and storage policies which will be automatically maintained throughout the lifecycle of the data. Heat Map skips internal access done for system tasks -- automatically excluding Stats Gathering, DDLs or Table Redefinitions.

Heat Map can be enabled as:

ALTER SYSTEM SET HEAT_MAP = ON;

By default the value is OFF

The V$HEAT_MAP_SEGMENT view displays real-time segment access information. The ALL_, DBA_, and USER_HEAT_MAP_SEGMENT views display the latest segment access time for all segments visible to the user. The ALL_, DBA_, and USER_HEAT_MAP_SEG_HISTOGRAM views display segment access information for all segments visible to the user. The DBA_HEATMAP_TOP_OBJECTS view displays heat map information for the top 1000 objects. The DBA_HEATMAP_TOP_TABLESPACES view displays heat map information for the top 100 tablespaces.