Oracle教程 2023-02-24

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

本站中文解释

Oracle视图DBA_HIST_PGA_TARGET_ADVICE包括关于监控历史PGA内存有关建议和结论的信息。

使用该视图，可以查询到关于PGA内存使用的建议和结论，例如PGA内存使用情况、PGA 目标建议、建议的比率等。主要信息包括：

• SNAP_ID：运行监控的时间点的SCN；

• INSTANCE_NUMBER：识别不同实例的唯一标识符；

• ADVICE_CATEGORY：对当前PGA内存使用情况的引导；

• ADVICE_NAME：针对数据库的PGA的建议；

• ADVICE_DESCRIPTION：建议的描述；

• ADVICE_STRING：建议和结论的详细信息；

• ADVICE_RATIO：记录 PGATARGET 和总PGA 内存建议比率；

• PGA_TARGET_FACTOR：记录PGA Target 建议因子；

• PGA_TARGET_ADVICE_MESSAGE：记录PGA Target 建议信息；

• PGA_TARGET_ADVICE_FOR_ESTIMATE：记录 PGATARGET 建议对于当前的估计。

要使用该视图，可以通过以下的SQL语句:

select advice_string,snap_id,instance_number,advice_category,advice_name,advice_ratio
from DBA_HIST_PGA_TARGET_ADVICE
where snap_id= and instance_number=;

其中，指定监控时间，指定实例号。

官方英文解释

DBA_HIST_PGA_TARGET_ADVICE displays historical predictions of how the cache hit percentage and over allocation count statistics displayed by the V$PGASTAT performance view would be impacted if the value of the PGA_AGGREGATE_TARGET parameter is changed.

This view contains snapshots of V$PGA_TARGET_ADVICE.

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
`PGA_TARGET_FOR_ESTIMATE`	`NUMBER`	`NOT NULL`	Value of `PGA_AGGREGATE_TARGET` for the prediction (in bytes)
`PGA_TARGET_FACTOR`	`NUMBER`		`PGA_TARGET_FOR_ESTIMATE` / the current value of the `PGA_AGGREGATE_TARGET` parameter
`ADVICE_STATUS`	`VARCHAR2(3)`		Indicates whether the advice is enabled (`ON`) or disabled (`OFF`) depending on the value of the `STATISTICS_LEVEL` parameter
`BYTES_PROCESSED`	`NUMBER`		Total bytes processed by all the work areas considered by this advice (in bytes)
`ESTD_TIME`	`NUMBER`		Time (in seconds) required to process the bytes
`ESTD_EXTRA_BYTES_RW`	`NUMBER`		Estimated number of extra bytes which would be read or written if `PGA_AGGREGATE_TARGET` was set to the value of the `PGA_TARGET_FOR_ESTIMATE` column. This number is derived from the estimated number and size of work areas which would run in one-pass (or multi-pass) for that value of `PGA_AGGREGATE_TARGET`.
`ESTD_PGA_CACHE_HIT_PERCENTAGE`	`NUMBER`		Estimated value of the cache hit percentage statistic when `PGA_AGGREGATE_TARGET` equals `PGA_TARGET_FOR_ESTIMATE`. This column is derived from the above two columns and is equal to `BYTES_PROCESSED` / (`BYTES_PROCESSED` + `ESTD_EXTRA_BYTES_RW`)
`ESTD_OVERALLOC_COUNT`	`NUMBER`		Estimated number of PGA memory over-allocations if the value of `PGA_AGGREGATE_TARGET` is set to `PGA_TARGET_FOR_ESTIMATE`. A nonzero value means that `PGA_TARGET_FOR_ESTIMATE` is not large enough to run the work area workload. Hence, `PGA_AGGREGATE_TARGET` should not be set to `PGA_TARGET_FOR_ESTIMATE` since Oracle will not be able to honor that target.
`CON_DBID`	`NUMBER`		The database ID of the PDB for the sampled session
`CON_ID`	`NUMBER`		The ID of the container that `CON_DBID` identifies. 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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