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安装AUTOTRACE报告（Setups Required for the AUTOTRACE Report）
要用这个特性，用户必须被赋予PLUSTRACE角色，而PLUSTRACE角色需要DBA来赋予。另外，该用户必须创建PLAN_TABLE表。
I. 首先创建PLUSTRACE角色并且赋给DBA： CONNECT sys/sys’s password AS SYSDBA @$ORACLE_HOME/sqlplus/admin/plustrce.sql
II. 赋权限给用户 CONNECT / AS SYSDBA
GRANT PLUSTRACE TO USER（预赋权的用户名）;
这样，就可以在该用户下设置AUTOTRACE报告的显示与否了。
AUTOTRACE报告中涉及到的两个方面的内容
I． SQL语句的执行计划
执行计划就是SQL优化器执行语句的查询执行顺序，每一行的执行计划都会有个行号，这个行号是连续的
II． SQL语句的数据库统计
数据库统计是服务器记录的执行当前的这条语句所需要的系统资源等，主要包括下表的内容
Database Statistic Name
Description
recursive calls
Number of recursive calls generated at both the user and system level. Oracle maintains tables used for internal processing. When Oracle needs to make a change to these tables, it internally generates an internal SQL statement, which in turn generates a recursive call.
db block gets
Number of times a CURRENT block was requested.
consistent gets
Number of times a consistent read was requested for a block.
physical reads
Total number of data blocks read from disk. This number equals the value of "physical reads direct" plus all reads into buffer cache.
redo size
Total amount of redo generated in bytes.
bytes sent via SQL*Net to client
Total number of bytes sent to the client from the foreground processes.
bytes received via SQL*Net from client
Total number of bytes received from the client over Oracle Net.
SQL*Net roundtrips to/from client
Total number of Oracle Net messages sent to and received from the client.
sorts (memory)
Number of sort operations that were performed completely in memory and did not require any disk writes.
sorts (disk)
Number of sort operations that required at least one disk write.
rows processed
Number of rows processed during the operation.
简单使用的例子：
SQL> show user
USER is "SYS"
（注：当前是sysdba用户）
（注：创建PLUSTRACE角色并且赋给DBA）
SQL> start $ORACLE_HOME/sqlplus/admin/plustrce.sql
（注：start 等价于@）
SQL> drop role plustrace;
drop role plustrace
*
ERROR at line 1:
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