Oracle 12c 中的Heat Map:
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.
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