在ORACLE数据库里，我们通常可以使用如下这些方法(包括但不限于)得到目标SQL的执行计划：
1，explain plan
2，DBMS_XPLAN包
3，SQLPLUS中的AUTOTRACE开关
4，10046事件
5，10053事件
6，AWR报告或者STATSPACK报告
前面的四种方法比较普遍。
下面我来介绍下第四种即10046事件如何得到目标SQL的执行计划
10046与使用explain plan命令，DBMS_XPLAN包和AUTOTRACE开关的不同之处在于，所得到的执行计划中明确显示了目标SQL的实际执行计划中每一个步骤所消耗的逻辑度(cr:consistent read)，物理读(pr:physical read)和花费的时间(time)。
用10046事件得到的目标SQL的执行计划只需要依次执行下面三步：
在当前SESSION中激活10046事件在此SESSION中执行目标SQL在此SESSION中关闭10046事件
执行完上面的步骤后，ORACLE会将目标SQL的执行计划和明细资源消耗写入此SESSION对应的TRACE文件中，此文件一把会在USER_DUMP_DEST目录下，其命名格式是： 实例名_ora_当前SESSION的SPID.trc.
通常可以用下面两种方法激活10046事件：
在当前SESSION中执行alter session set events '10046 trace name context forever,level 12'在当前SESSION中执行oradebug event 10046 trace name context forever,level 12
本人偏向喜欢用第二中，因为可以在激活10046事件后，执行命令oradebug tracefile_name来得到当前SESSION所对应的trace文件的具体路径和名称
对应的在当前SESSION中关闭10046事件的方法为：
alter session set events '10046 trace name context off'oradebug event 10046 trace name context off
10046生成的TRACE文件，我们称之为裸文件(raw trace),ORACCLE 提供了工具TKPROF来查看他。下面我们来做一个实验来演示如何通过10046事件来获取和查看目标SQL的实际执行计划
下面我以目标SQL： "select empno,ename,dname from scott.emp,scott.dept where emp.deptno=dept.deptno" 为例子来说明10046事件和TKPROF的用法
SQL> oradebug help
HELP [command] Describe one or all commands
SETMYPID Debug current process
SETOSPID Set OS pid of process to debug
SETORAPID ['force'] Set Oracle pid of process to debug
SHORT_STACK Dump abridged OS stack
DUMP [addr] Invoke named dump
DUMPSGA [bytes] Dump fixed SGA
DUMPLIST Print a list of available dumps
EVENT Set trace event in process
SESSION_EVENT Set trace event in session
DUMPVAR [level] Print/dump a fixed PGA/SGA/UGA variable
DUMPTYPE Print/dump an address with type info
SETVAR Modify a fixed PGA/SGA/UGA variable
PEEK [level] Print/Dump memory
POKE Modify memory
WAKEUP Wake up Oracle process
SUSPEND Suspend execution
RESUME Resume execution
FLUSH Flush pending writes to trace file
CLOSE_TRACE Close trace file
TRACEFILE_NAME Get name of trace file
LKDEBUG Invoke global enqueue service debugger
NSDBX Invoke CGS name-service debugger
-G Parallel oradebug command prefix
-R Parallel oradebug prefix (return output
SETINST Set instance list in double quotes
SGATOFILE Dump SGA to file; dirname in double quotes
DMPCOWSGA Dump & map SGA as COW; dirname in double quotes
MAPCOWSGA Map SGA as COW; dirname in double quotes
HANGANALYZE [level] [syslevel] Analyze system hang
FFBEGIN Flash Freeze the Instance
FFDEREGISTER FF deregister instance from cluster
FFTERMINST Call exit and terminate instance
FFRESUMEINST Resume the flash frozen instance
FFSTATUS Flash freeze status of instance
SKDSTTPCS Helps translate PCs to names
WATCH Watch a region of memory
DELETE watchpoint Delete a watchpoint
SHOW watchpoints Show watchpoints
CORE Dump core without crashing process
IPC Dump ipc information
UNLIMIT Unlimit the size of the trace file
PROCSTAT Dump process statistics
CALL [arg1] ... [argn] Invoke function with arguments
SQL> oradebug setmypid
Statement processed.
SQL> oradebug event 10046 trace name context forever,level 12
Statement processed.
SQL> select empno,ename,dname from scott.emp,scott.dept where emp.deptno=dept.deptno;
EMPNO ENAME DNAME
---------- ---------- --------------
7369 SMITH RESEARCH
7499 ALLEN SALES
7521 WARD SALES
7566 JONES RESEARCH
7654 MARTIN SALES
7698 BLAKE SALES
7782 CLARK ACCOUNTING
7788 SCOTT RESEARCH
7839 KING ACCOUNTING
7844 TURNER SALES
7876