Oracle数据库的实时SQL监控能让你用来监控正在执行SQL语句的性能。缺省情况下，当SQL语句使用 并行执行或当SQL语句的单个操作消耗了5秒的CPU或I/O时间就会自动启动SQL监控。可以使用v $sql_monitor与v$sql_plan_monitor视图来监控SQL语句执行的统计信息。可以使用这些视图时行关 联来获得被监控到的关于执行的其它信息:
.v$active_session_history
.v$session
.v$session_longops
.v$sql
.v$sql_plan
在监控初始化之后，数据库将会向动态性能视图v$sql_monitor中增加条目。这个条目跟踪SQL执行的 关键性能，包括：执行时间，CPU时间，读取与写入的次数，I/O等待时间和各种其它等待时间。这些 统计信息当SQL语句执行时间会被实时刷新，每秒生成一次。在执行结束后，监控信息不会立即被删 除，但在v$sql_monitor中至少保留一分钟。当需要为新的SQL语句腾出空间时，会评估条目是否需要 被删除来回收空间。
v$sql_monitor视图包含v$sql视图中统计信息的一组子集。然而，不像v$sql，监控统计信息不会对 多次执行进行累加。相反，v$sql_monitor中的一个条目被关联到SQL语句的一个单独操作。如果数据 库监控相同SQL语句执行两次，那么在v$sql_monitor中会有两次执行的统计信息。
为了唯一标识相同SQL语句的两次执行，会生成一个叫执行键的复合键。执行键是由三个属性组成， 它们分别为v$sql_monitor中的:
.SQL标识符用来标识SQL语句(SQL_ID)
.开始执行时间(SQL_EXEC_START)
.一个内部生成的标识符用来确保主键是唯一的(SQL_EXEC_ID)
SQL执行计划监控
真时SQL监控也包括监控SQL语句的执行计划中的每一个操作的统计信息。这些数据在v $sql_plan_monitor视图中可以看到。类似于v$sql_monitor视图，v$sql_plan_monitor视图中的统计 信息当SQL语句被执行时每秒会更新一次。这些统计信息在SQL执行结束后是存在的，它的生命周期与 v$sql_monitor是一样的。对于每个被监控的SQL语句，在v$sql_plan_monitor视图中将会有多个条目 ，每个条目关联执行计划中的一个操作。
并行执行监控
Oracle数据库会当SQL语句开始执行时会自动监控并行查询，DML与DDL语句。v$sql_monitor与v $sql_plan_monitor视图将会以单独的条目来记录并行执行中每个操作的监控信息。
v$sql_monitor对于并行执行协调进程和每个并行执行服务器进程有一个条目。对于每一个条目在v $sql_plan_monitor视图中也有相关的条目。因为对于SQL语句并行执行的所分配的进程是相互协作的 ，这些条目共享相同的执行键（由sql_id,sql_exec_start与sql_exec_id组成）。因此可以聚合执行 键来判断并行执行的整个统计信息。
生成SQL监控报告
可以使用SQL监控报告来查看SQL监控数据。SQL监控报告使用以下视图中的数据:
.gv$sql_monitor
.gv$sql_plan_monitor
.gv$sql
.gv$sql_plan
.gv$active_session_history
.gv$session_longops
为了生成SQL监控报告，运行dbms_sqltune.report_sql_monitor过程:
SQL> set long 10000000
SQL> set longchunksize 10000000
SQL> set linesize 200
SQL> variable my_rept clob;
SQL> begin
2 :my_rept:=dbms_sqltune.report_sql_monitor();
3 end;
4 /
print :my_rept
PL/SQL procedure successfully completed.
SQL>
MY_REPT
---------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------- ------------------------
SQL Monitoring Report
SQL Text
------------------------------
/* SQL Analyze(1) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) dbms_stats cursor_sharing_exact use_weak_name_resl dynamic_sampling(0) no_monitoring no_substrb_pad */to_char(count("AAE064"
)),to_char(substrb(dump(min("AAE064"),16,0,32),1,120)),to_char(substrb(dump(max ("AAE064"),16,0,32),1,120)),to_char(count("AAB001")),to_char(substrb(dump(min ("AAB001"),16,0,32),1,120)),to_char(substrb(
dump(max("AAB001"),16,0,32),1,120)),to_char(count("AAB191")),to_char(substrb(dump(min ("AAB191"),16,
0,32),1,120)),to_char(substrb(dump(max("AAB191"),16,0,32),1,120)),to_char(count ("AAB190")),to_char(substrb(dump(min("AAB190"),16,0,32),1,120)),to_char(substrb(dump (max("AAB190"),16,0,32),1,120)),to_ch
ar(count("AAB211")),to_char(substrb(dump(min("AAB211"),16,0,32),1,120)),to_char(substrb (dump(max("AAB211"),16,0,32),1,120)),to_char(count("AAB212")),to_char(substrb(dump(min ("AAB212"),16,0,32),1,120))
,to_char(substrb(dump(max("AAB212"),16,0,32),1,120)),to_char(count("AAB213")),to_char (substrb(dump(
min("AAB213"),16,0,32),1,120)),to_char(substrb(dump(max ("AAB213"),16,0,32),1,120)),to_char(count("AAB214")),to_char(substrb(dump(min ("AAB214"),16,0,32),1,120)),to_char(substrb(dump(max("AAB214"),16,0,
32),1,120)),to_char(count("AAB215")),to_char(substrb(dump(min ("AAB215"),16,0,32),1,120)),to_char(substrb(dump(max("AAB215"),16,0,32),1,120)),to_char (count("AAE011")),to_char(substrb(dump(min("AAE011")
,16,0,32),1,120)),to_char(substrb(dump(max("AAE011"),16,0,32),1,120)),to_char(count ("AAE036")),to_c
har(substrb(dump(min("AAE036"),16,0,32),1,120)),to_char(substrb(dump(max ("AAE036"),16,0,32),1,120)),to_char(count("AAE017")),to_char(substrb(dump(min ("AAE017"),16,0,32),1,120)),to_char(substrb(dump(ma
x("AAE017"),16,0,32),1,120)),to_char(count("SJCQNY")),to_char(substrb(dump(min ("SJCQNY"),16,0,32),1,120)),to_char(substrb(dump(max("SJCQNY"),16,0,32),1,120)) from "LEMIS_4307"."AB13" t /*
NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV, NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL*/
Global Information
------------------------------
Status : DONE (ALL ROWS)
Instance ID : 1
Session : SYS (1837:1553)
SQL ID : 5k014mmtyr7qw
SQL Execution ID : 16777216
Execution Started : 10/17/2016 22:02:26
First Refresh Time : 10/17/2016 22:02:32
Last Refresh Time : 10/17/2016 22:02:55
Duration : 29s
Module/Action : DBMS_SCHEDULER/ORA$AT_OS_OPT_SY_1
Service : SYS$USERS
Program : oracle@sjjh (J001)
Fetch Calls : 1
Global Stats
=================================================
| Elapsed | Cpu | Other | Fetch | Buffer |
| Time(s) | Time(s) | Waits(s) | Calls | Gets |
=================================================
| 28 | 28 | 0.09 | 1 | 307K |
=================================================
SQL Plan Monitoring Details (Plan Hash Value=3367417341)
======================================================================================== ===========================================
| Id | Operation | Name | Rows | Cost | Time | Start | Execs | Rows | Activity | Activity Detail |
| | | | (Estim) | | Active(s) | Active | | (Actual) | (%) | (# samples) |
======================================================================================== ===========================================
| 0 | SELECT STATEMENT | | | | 24 | +6 | 1 | 1 | | |
| 1 | SORT AGGREGATE | | 1 | | 28 | +2 | 1 | 1 | 34.48 | Cpu (10) |
| 2 | APPROXIMATE NDV AGGREGATE | | 29M | 89482 | 29 | +1 | 1 | 27M | 55.17 | Cpu (16) |
| 3 | TABLE ACCESS FULL | AB13 | 29M | 89482 | 25 | +5 | 1 | 29M | 10.34 | Cpu (3) |
======================================================================================== ===========================================
dbms_sqltune.report_sql_monitor过程接受几种输入参数来指定执行，报告的详细级别与报告类型 ('TEXT','HTML'或'XML')。缺省情况下，如果没有指定参数将会对最后所监控的到SQL生成文本类型 的SQL监控报告。
SQL> desc dbms_sqltune.report_sql_monitor
Parameter Type Mode Default?
------------------- -------- ---- --------
(RESULT) CLOB
SQL_ID VARCHAR2 IN Y
SESSION_ID NUMBER IN Y
SESSION_SERIAL NUMBER IN Y
SQL_EXEC_START DATE IN Y
SQL_EXEC_ID NUMBER IN Y
INST_ID NUMBER IN Y
START_TIME_FILTER DATE IN Y
END_TIME_FILTER DATE IN Y
INSTANCE_ID_FILTER NUMBER IN Y
PARALLEL_FILTER VARCHAR2 IN Y
PLAN_LINE_FILTER NUMBER IN Y
EVENT_DETAIL VARCHAR2 IN Y
BUCKET_MAX_COUNT NUMBER IN Y
BUCKET_INTERVAL NUMBER IN Y
BASE_PATH VARCHAR2 IN Y
LAST_REFRESH_TIME DATE IN Y
REPORT_LEVEL VARCHAR2 IN Y
TYPE VARCHAR2 IN Y
SQL_PLAN_HASH_VALUE NUMBER IN Y
也可以使用以下方式来生成SQL监控报告:
SQL> set long 10000000
SQL> set longchunksize 10000000
SQL> set linesize 200
SQL> select dbms_sqltune.report_sql_monitor from dual;
REPORT_SQL_MONITOR
---------------------------------------------------------------------------------------- ---------------------------------------------------------------------------------------- ------------------------
SQL Monitoring Report
SQL Text
------------------------------
/* SQL Analyze(1) */ select /*+ full(t) no_parallel(t) no_parallel_index(t) dbms_stats cursor_sharing_exact use_weak_name_resl dynamic_sampling(0) no_monitoring no_substrb_pad */to_char(count("MONEY_N
O")),to_char(substrb(dump(min("MONEY_NO"),16,0,32),1,120)),to_char(substrb(dump(max ("MONEY_NO"),16,0,32),1,120)),to_char(count("PAY_INFO_NO")),to_char(substrb(dump(min ("PAY_INFO_NO"),16,0,32),1,120)),
to_char(substrb(dump(max("PAY_INFO_NO"),16,0,32),1,120)),to_char(count ("PAY_MONEY")),to_char(substr
b(dump(min("PAY_MONEY"),16,0,32),1,120)),to_char(substrb(dump(max ("PAY_MONEY"),16,0,32),1,120)),to_char(count("MONEY_TYPE")),to_char(substrb(dump(min ("MONEY_TYPE"),16,0,32),1,120)),to_char(substrb(dum
p(max("MONEY_TYPE"),16,0,32),1,120)),to_char(count("CALC_MAN_SUM")),to_char(substrb (dump(min("CALC_MAN_SUM"),16,0,32),1,120)),to_char(substrb(dump(max ("CALC_MAN_SUM"),16,0,32),1,120)),to_char(count("C
ALC_BASE")),to_char(substrb(dump(min("CALC_BASE"),16,0,32),1,120)),to_char(substrb(dump (max("CALC_B
ASE"),16,0,32),1,120)),to_char(count("MONEY_ID")),to_char(substrb(dump(min ("MONEY_ID"),16,0,32),1,120)),to_char(substrb(dump(max ("MONEY_ID"),16,0,32),1,120)),to_char(count("CORP_ID")),to_char(substrb(
dump(min("CORP_ID"),16,0,32),1,120)),to_char(substrb(dump(max ("CORP_ID"),16,0,32),1,120)),to_char(count("PAYED_MONEY")),to_char(substrb(dump(min ("PAYED_MONEY"),16,0,32),1,120)),to_char(substrb(dump(ma
x("PAYED_MONEY"),16,0,32),1,120)),to_char(count("CALC_PRD")),to_char(substrb(dump(min ("CALC_PRD"),1
6,0,32),1,120)),to_char(substrb(dump(max("CALC_PRD"),16,0,32),1,120)),to_char(count ("SRC_TYPE")),to_char(substrb(dump(min("SRC_TYPE"),16,0,32),1,120)),to_char(substrb (dump(max("SRC_TYPE"),16,0,32),1,1
20)),to_char(count("PAYED_FLAG")),to_char(substrb(dump(min ("PAYED_FLAG"),16,0,32),1,120)),to_char(substrb(dump(max("PAYED_FLAG"),16,0,32),1,120)) from "SJGX_YB"."LV_CROPFUNDPAR" t /*
ACL,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV, NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL,NDV,NIL,NIL*/
Global Information
------------------------------
Status : DONE (ALL ROWS)
Instance ID : 1
Session : SYS (146:19)
SQL ID : 6sbw88979vmcv
SQL Execution ID : 16777216
Execution Started : 10/18/2016 22:01:04
First Refresh Time : 10/18/2016 22:01:11
Last Refresh Time : 10/18/2016 22:01:38
Duration : 34s
Module/Action : DBMS_SCHEDULER/ORA$AT_OS_OPT_SY_4
Service : SYS$USERS
Program : oracle@sjjh (J001)
Fetch Calls : 1
Global Stats
=================================================
| Elapsed | Cpu | Other | Fetch | Buffer |
| Time(s) | Time(s) | Waits(s) | Calls | Gets |
=================================================
| 34 | 34 | 0.11 | 1 | 294K |
=================================================
SQL Plan Monitoring Details (Plan Hash Value=3534073399)
======================================================================================== =====================================================
| Id | Operation | Name | Rows | Cost | Time | Start | Execs | Rows | Activity | Activity Detail |
| | | | (Estim) | | Active(s) | Active | | (Actual) | (%) | (# samples) |
======================================================================================== =====================================================
| 0 | SELECT STATEMENT | | | | 28 | +7 | 1 | 1 | | |
| 1 | SORT AGGREGATE | | 1 | | 33 | +2 | 1 | 1 | 40.00 | Cpu (14) |
| 2 | APPROXIMATE NDV AGGREGATE | | 24M | 80111 | 35 | +0 | 1 | 39M | 54.29 | Cpu (19) |
| 3 | MAT_VIEW ACCESS FULL | LV_CROPFUNDPAR | 24M | 80111 | 28 | +7 | 1 | 39M | 2.86 | Cpu (1) |
======================================================================================== =====================================================
在Global Information部分，Status显示为DONE，说明SQL语句已经执行完成了。Time Active(s)列 显示操作已经执行了多长时间。Start Active列，以秒为单位，代表SQL语句执行的开始。在这个报 告中，MAT_VIEW ACCESS FULL是ID 3是第一个被执行的(+7s Start Active)并且执行了28秒。
Start列显示该操作被执行的次数。Rows(Actual)列显示被处理的行数，Rows(Estim)列显示优化器所 评估的行数。Memory与Temp列指示每个操作所消耗的内存与临时空间的大小。
Activity(percent)与Activity Detail(sample #)是通过连接v$sql_plan_monitor与v $active_session_history视图而得到。Activity(percent)显示执行计划中每个操作所占数据库时间 的百分比。Activity Detail(sample#)显示了活动的属性(比如CPU或等待事件)。在这个报告中，ID 2消耗了的数据库时间百分比为54.29%（APPROXIMATE NDV AGGREGATE）。活动由19samples组成。最 后一列,Progress,显示了v$session_longops视图所监控到的操作信息。
启用与禁用SQL监控
SQL监控功能当statistics _level参数被设置为all或typical(缺省值)时缺省是开启的。额外， control_management_pack_access参数必须设置为diagnostic+tuning(缺省值),因为SQL监控是 Oracle数据库优化包的一个功能。SQL监控对于所有运行时间长的查询会自动启动。
有两种语句级别的hint可以用来强制或者阻止SQL语句被监控。为了强制SQL监控，使用monitor hint:
select /*+ MONITOR */ from dual;
这种hint只有当control_management_pack_access参数被设置为diagnostic+tuning时才生效。为了 阻止SQL语句被监控可以使用no_monitor hint。
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