Oracle教程 2023-02-24

Oracle 视图 DBA_HIST_SGA_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_SGA_TARGET_ADVICE用于针对SGA组件自动估算（Auto Estimate）和有效内存指示器（Effective Memory Advisor）来查看推荐的SGA大小。该视图可以帮助DBA以及系统管理员估计SGA大小，并可以查看缓存的命中率以及应该将内存分配给每个组件的数量。共享池的指令（parameter command）可以对于自动参数设置（Auto Tuning）组件以及按照推荐的值来重新调整SGA组件的大小。

使用方法为：

1.在DBA_HIST_SGA_TARGET_ADVICE视图中运行以下查询，以显示估算的SGA大小，以及推荐的SGA组件大小：

SELECT * FROM DBA_HIST_SGA_TARGET_ADVICE;

2.运行以下查询，显示出每个组件的推荐大小：

SELECT pool, name, bytes_cached, recommended_size
FROM DBA_HIST_SGA_TARGET_ADVICE
WHERE pool IN (‘shared_pool’,’large_pool’,’java_pool’,’streams_pool’);

3.使用Oracle指令或是运行alter system来调整每个缓存池的大小，按照DBA_HIST_SGA_TARGET_ADVICE视图中推荐的值来重新调整SGA组件的大小。

官方英文解释

DBA_HIST_SGA_TARGET_ADVICE provides historical information about the SGA_TARGET initialization parameter.

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
`SGA_SIZE`	`NUMBER`	`NOT NULL`	Size of the SGA
`SGA_SIZE_FACTOR`	`NUMBER`	`NOT NULL`	Ratio between the `SGA_SIZE` and the current size of the SGA
`ESTD_DB_TIME`	`NUMBER`	`NOT NULL`	Estimated DB_TIME for this SGA_SIZE
`ESTD_PHYSICAL_READS`	`NUMBER`		Estimated number of physical reads
`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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