Oracle的Recursive Call理解

Recursive Calls：  Number of recursive calls generated at both the user and system level.   

Oracle Database maintains tables used for internal processing. When it needs to change these tables, Oracle Database generates an internal SQL statement, which in turn generates a recursive call. In short, recursive calls are basically SQL performed on behalf of your SQL. So, if you had to parse the query, for example, you might have had to run some other queries to get data dictionary information. These would be recursive calls. Space management, security checks, calling PL/SQL from SQL—all incur recursive SQL calls。
 DB Block Gets： Number of times a CURRENT block was requested.

 

Cost ：是对CPU的占比

Cardinality：是对返回的集合数的行数