Oracle教程 2023-02-26

Oracle 视图 DBA_HIST_BASELINE 官方解释，作用，如何使用详细说明

本站中文解释

及用途

Oracle的视图DBA_HIST_BASELINE视图显示当前活动的所有基线的信息。它主要用于收集和跟踪定期在数据库上运行的SQL和AWR快照之间的差异。它可以帮助数据库管理员了解数据库结构和SQL查询性能的变化情况。

DBA_HIST_BASELINE视图中包含的字段，如下：
– BASELINE_ID: 基线ID
– BASELINE_NAME：基线名称
– BASELINE_TYPE：基线类型，有可能是SYSTEM_TIME或者SYSTEM_CHANGE_NUMBER
– BEGIN_INTERVAL_TIME：BEGIN记录的开始时间
– END_INTERVAL_TIME：END记录的结束时间
– SCN_NUMBER：BEGIN记录的系统改变号的编号
– \_IDENTIFIER：标识基线的唯一标识符
– ENABLE：是否启用基线
– PERIOD：基线的建立周期

使用方法：为了评估性能变化，可以使用DBA_HIST_BASELINE视图去查看历史基线，并做性能分析，并可以修改查询方式和SQL语句去优化性能。

官方英文解释

DBA_HIST_BASELINE displays information on baselines taken in the system.

For each baseline, this view displays the complete time range and whether the baseline is the default baseline.

Column	Datatype	Description
`DBID`	`NUMBER`	Database ID
`BASELINE_ID`	`NUMBER`	Internal ID for the baseline
`BASELINE_NAME`	`VARCHAR2(64)`	User-specified name for the baseline
`BASELINE_TYPE`	`VARCHAR2(13)`	The baseline type, as follows: `STATIC` – baselines that are created manually by the user `MOVING WINDOW` – baselines that have dynamic start and end snapshot IDs `GENERATED` – baselines that are automatically generated by the system, using a template
`START_SNAP_ID`	`NUMBER`	Start snapshot ID for the baseline
`START_SNAP_TIME`	`TIMESTAMP(3)`	Time associated with the start snapshot ID
`END_SNAP_ID`	`NUMBER`	End snapshot ID for the baseline
`END_SNAP_TIME`	`TIMESTAMP(3)`	Time associated with the end snapshot ID
`MOVING_WINDOW_SIZE`	`NUMBER`	If `BASELINE_TYPE` is `MOVING WINDOW`, this field is the size of the moving window in number of days. If NULL, then the window size is the value of the AWR retention setting.
`CREATION_TIME`	`DATE`	Time the baseline was created
`EXPIRATION`	`NUMBER`	How long to keep the baseline, in number of days. A NULL value means that the baseline will be kept forever.
`TEMPLATE_NAME`	`VARCHAR2(64)`	Name of the template that created this baseline, if any.
`LAST_TIME_COMPUTED`	`DATE`	Last time that statistics were computed on the baseline.
`CON_ID`	`NUMBER`	The ID of the container to which the data pertains. Possible values include: `0`: This value is used for rows containing data that pertain to the entire CDB. This value is also used for rows in non-CDBs. `1`: This value is used for rows containing data that pertain to only the root n: Where n is the applicable container ID for the rows containing data

数据运维技术 » Oracle 视图 DBA_HIST_BASELINE 官方解释，作用，如何使用详细说明

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