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

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本站中文解释

Oracle视图DBA_HIST_ASH_SNAPSHOT存储数据库应用程序自任务跟踪使用的信息，可以帮助DBA以窗口方式查看系统上活动的会话以及其执行的任务的性能。这个视图内的数据基于任务跟踪（AWR）报告的任务快照采样器数据收集的，可以帮助识别会话中正在执行的任务，滚动及重复任务。

使用时，首先要执行oracle脚本dbms_scheduler.create_snapshot来创建任务跟踪快照，采样时间可以根据实际情况进行调整，但不能小于15秒以下，然后查看DBA_HIST_ASH_SNAPSHOT 视图中的数据，根据任务的SQL_ID字段把任务的SQL文件和相关执行结果查询出来，根据这些信息就可以进行性能分析并得出解决方案了。

官方英文解释

DBA_HIST_ASH_SNAPSHOT provides the list of snapshots that contains Active Session History (ASH) data.

This view differs from DBA_HIST_SNAPSHOT in that it provides snapshots which had errors flushing some Automatic Workload Repository (AWR) tables, but for which ASH data may be successfully flushed (DBA_HIST_SNAPSHOT filters out snapshots which had errors flushing AWR tables).

Column	Datatype	NULL	Description
`SNAP_ID`	`NUMBER`	`NOT NULL`	Unique snapshot ID
`DBID`	`NUMBER`	`NOT NULL`	Database ID for the snapshot
`INSTANCE_NUMBER`	`NUMBER`	`NOT NULL`	Instance number for the snapshot
`STARTUP_TIME`	`TIMESTAMP(3)`	`NOT NULL`	Startup time of the instance
`BEGIN_INTERVAL_TIME`	`TIMESTAMP(3)`	`NOT NULL`	Time at the beginning of the snapshot interval
`END_INTERVAL_TIME`	`TIMESTAMP(3)`	`NOT NULL`	Time at the end of the snapshot interval; the actual time the snapshot was taken
`FLUSH_ELAPSED`	`INTERVAL DAY(5) TO SECOND(1)`		Amount of time to perform the snapshot
`SNAP_LEVEL`	`NUMBER`		Snapshot level
`STATUS`	`NUMBER`		Indicates if the snapshot was successfully flushed without any errors. Possible values: `0` – No errors `1` – Errors on some AWR tables
`ERROR_COUNT`	`NUMBER`		Number of errors occurring in the tables for the particular snapshot
`BL_MOVED`	`NUMBER`		Reserved for internal use
`SNAP_FLAG`	`NUMBER`		Condition under which the snapshot was inserted. Possible values are: `1` – Manual snapshot created using a PL/SQL package `2` – Imported snapshot `4` – Snapshot taken while Diagnostic Pack or Tuning Pack was not enabled
`SNAP_TIMEZONE`	`INTERVAL DAY(0) TO SECOND(0)`		Snapshot time zone expressed as offset from UTC (Coordinated Universal Time) time zone
`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

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

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官方英文解释