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

Oracle视图 DBA_COMPARISON_SCAN 是Oracle高级安全特性「比较扫描」的概念实现，主要用来记录数据库对象上执行SQL比较操作的记录。主要信息包括：比较操作发起者、比较操作执行时间、比较操作执行查询、比较操作执行结果等信息。

使用 DBA_COMPARISON_SCAN 视图，可以通过数据库函数 DBMS_COMPARISON 来比较数据库对象的状态，进而检查数据库是否有变更，以便及时采取必要的响应措施，保证数据库安全。

要使用DBA_COMPARISON_SCAN视图，必须先执行DBMS_COMPARISON模块中的COMPARISON函数，将比较信息记录在视图中，然后才能检索出与比较操作相关的信息。

DBA_COMPARISON_SCAN displays information about all comparison scans in the database.

Related View

USER_COMPARISON_SCAN displays information about the comparison scans owned by the current user. This view does not display the OWNER column.

Column	Datatype	NULL	Description
`OWNER`	`VARCHAR2(128)`	`NOT NULL`	Owner of the comparison scan
`COMPARISON_NAME`	`VARCHAR2(128)`	`NOT NULL`	Name of the comparison scan
`SCAN_ID`	`NUMBER`	`NOT NULL`	Scan ID
`PARENT_SCAN_ID`	`NUMBER`		Scan ID of the immediate parent scan
`ROOT_SCAN_ID`	`NUMBER`		Scan ID of the root (top-most) parent
`STATUS`	`VARCHAR2(16)`		Status of the scan: `SUC` `BUCKET DIF` `FINAL BUCKET DIF` `ROW DIF`
`CURRENT_DIF_COUNT`	`NUMBER`		Current cumulative (including children) diff count of the scan
`INITIAL_DIF_COUNT`	`NUMBER`		Initial cumulative (including children) diff count of the scan
`COUNT_ROWS`	`NUMBER`		Number of rows in the scan
`SCAN_NULLS`	`VARCHAR2(1)`		Indicates whether NULLs are part of this scan (`Y`) or not (`N`)
`LAST_UPDATE_TIME`	`TIMESTAMP(6)`		Time that this row was last updated