Oracle 11g RAC跨实例控制并行

在Oracle 10g RAC中的并行执行是由两个参数来控制的:instance_groups和parallel_instance_group这两个参数在Oracle 10g RAC中必须同时设置。

instance_groups可以有多个值但是静态值,parallel_instance_group可以在系统级别与会话级别进行修改。

在Oracle 10g RAC中,为了使用并行执行需要设置parallel_instance_group参数,并且parallel_instance_group的值必须是该实例instance_groups所指定的参数值之一。

例如,有一个3节点的Oracle 10g RAC在spfile中有以下设置:
myrac1.instance_groups=’rac’,’rac1′
myrac2.instance_groups=’rac’,’rac2′
myrac3.instance_groups=’rac’,’rac3′
myrac1.parallel_instance_group=’rac1’#节点1的并行执行只能在节点1上运行
myrac2.parallel_instance_group=’rac2’#节点2的并行执行只能在节点2上运行
myrac3.parallel_instance_group=’rac3’#节点3的并行执行只能在节点3上运行

在11gRAC中,因为向后兼容仍然可以使用instance_groups和parallel_instance_group参数。然而,在Oracle 11g RAC中不需要这样做,instance_groups参数已经被废弃并且保留只是为了向后兼容。

在Oracle 11gRAC中并行查询子进程与服务集成在一起,因此不需要再设置instance_groups和parallel_instance_group参数。因为不需要设置instance_groups参数,而是可以直接设置服务名,
例如:alter session set parallel_instance_group=service_name。因为在11g中instance_groups参数已经被废弃,可以继续使用,但是它只是为了向后兼容。

在Oracle 11g RAC中也可以不需要设置parallel_instance_groups参数来限制并行查询子进程在指定的实例上运行。如果以并行方式来执行SQL语句,那么缺省情况下并行进程只会在你通过服务名所连接到的数据库实例上运行。这不会影响其它的并行操作比如并行恢复或gv$视图的查询处理。为了覆盖这种行为,可以设置parallel_instance_group参数。

可以使用srvctl add service命令来创建服务。例如,数据库名是rac且有2个实例,rac1和rac2。
对每个实例创建一个服务

[grid@rac1 ~]$ srvctl add service -d rac -s rac1 -r rac1 -a rac2
[grid@rac1 ~]$ srvctl add service -d rac -s rac2 -r rac2 -a rac1
[grid@rac1 ~]$ srvctl start service -d rac -s rac1
[grid@rac1 ~]$ srvctl start service -d rac -s rac2

上面的语句将创建两个服务,每个实例一个,-r参数指定首选实例,-a参数指定可用实例。
1.如果使用其中的一个服务连接数据库,并且没有显式地设置parallel_instance_groups参数,那么并行执行将被限制在你的连接的实例上执行

例如,如果连接到rac1,因上连接到rac1实例,那么并行查询了进程将只能在rac1的r参数所指定的实例rac1上运行。

SQL> conn sys/system@rac1 as sysdba

SQL> select instance_name from v$instance;

INSTANCE_NAME
----------------
rac1

SQL> show parameter parallel_instance_group

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string
SQL> show parameter instance_groups

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
instance_groups                      string

SQL> show parameter parallel_degree_policy

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_degree_policy               string      auto
SQL> set timing on
SQL> set autotrace on
SQL> select /*+ parallel(t1,60) */ count(*) from t1;

  COUNT(*)
----------
  11121536

Elapsed: 00:00:41.25

Execution Plan
----------------------------------------------------------
Plan hash value: 3110199320

--------------------------------------------------------------------------------
------------------------

| Id  | Operation              | Name     | Rows  | Cost (%CPU)| Time     |    T
Q  |IN-OUT| PQ Distrib |

--------------------------------------------------------------------------------
------------------------

|   0 | SELECT STATEMENT       |          |     1 |   793   (0)| 00:00:01 |
   |      |            |

|   1 |  SORT AGGREGATE        |          |     1 |            |          |
   |      |            |

|   2 |   PX COORDINATOR       |          |       |            |          |
   |      |            |

|   3 |    PX SEND QC (RANDOM) | :TQ10000 |     1 |            |          |  Q1,
00 | P->S | QC (RAND)  |

|   4 |     SORT AGGREGATE     |          |     1 |            |          |  Q1,
00 | PCWP |            |

|   5 |      PX BLOCK ITERATOR |          |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWC |            |

|   6 |       TABLE ACCESS FULL| T1       |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWP |            |

--------------------------------------------------------------------------------
------------------------


Note
-----
   - dynamic sampling used for this statement (level=2)
   - Degree of Parallelism is 60 because of hint


Statistics
----------------------------------------------------------
        430  recursive calls
          0  db block gets
     281608  consistent gets
     158184  physical reads
       3328  redo size
        425  bytes sent via SQL*Net to client
        419  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
         21  sorts (memory)
          0  sorts (disk)
          1  rows processed

在执行时查询并行子进程的是否只在rac1上运行

SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like ('PX%') ORDER BY 1;

   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1         29 PX Deq: Execution Msg                                                    54  268566527          1 1113052640         -1
         1        105 PX Deq: Execution Msg                                                     2  268566527          1 1113043256         -1
         1         43 PX Deq: Execution Msg                                                    57  268566527          1 1113057500          0
         1         44 PX Deq: Execution Msg                                                    55  268566527          1 1011415624         -1
         1         50 PX Deq: Execution Msg                                                    45  268566527          1 1113065368         -1
         1         53 PX Deq: Execution Msg                                                    64  268566527          1 1113070008          0
         1         54 PX Deq: Execute Reply                                                  8603        200          1          0          0
         1         55 PX Deq: Execution Msg                                                    59  268566527          1 1113049700         -1
         1         62 PX Deq: Execution Msg                                                    68  268566527          1 1113067520          0
         1         69 PX Deq: Execution Msg                                                    53  268566527          1 1113068028          0
         1         74 PX Deq: Execution Msg                                                    60  268566527          1 1113066504         -1

   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1         79 PX Deq: Execute Reply                                                   641        200          1          0          0
         1         80 PX Deq: Execution Msg                                                    59  268566527          1 1113068568         -1
         1         81 PX Deq: Execution Msg                                                    63  268566527          1 1113069048         -1
         1         88 PX Deq: Execution Msg                                                    59  268566527          1 1113051680          0
         1         97 PX Deq: Execution Msg                                                    46  268566527          1 1011409340          0


16 rows selected.

可以看到并行子进程全都是在实例rac1上运行。

2.一旦创建这些服务名之后,服务名rac1和rac2可以作为parallel_instance_groups的参数值,不管你使用那个服务名来进行数据库连接例如,如果使用通用的数据库服务名rac来进行连接,发现连接到了rac1实例,那么并行子进程会在当前所连接的实例或所有实例上运行。

SQL> conn sys/system@rac as sysdba

SQL> select instance_name from v$instance;

INSTANCE_NAME
----------------
rac1

SQL> show parameter parallel_instance_group

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string
SQL> show parameter instance_groups

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
instance_groups                      string

SQL> show parameter parallel_degree_policy

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_degree_policy               string      auto
SQL> set timing on
SQL> set autotrace on
SQL> select /*+ parallel(t1,60) */ count(*) from t1;

  COUNT(*)
----------
  11121536

Elapsed: 00:00:41.25

Execution Plan
----------------------------------------------------------
Plan hash value: 3110199320

--------------------------------------------------------------------------------
------------------------

| Id  | Operation              | Name     | Rows  | Cost (%CPU)| Time     |    T
Q  |IN-OUT| PQ Distrib |

--------------------------------------------------------------------------------
------------------------

|   0 | SELECT STATEMENT       |          |     1 |   793   (0)| 00:00:01 |
   |      |            |

|   1 |  SORT AGGREGATE        |          |     1 |            |          |
   |      |            |

|   2 |   PX COORDINATOR       |          |       |            |          |
   |      |            |

|   3 |    PX SEND QC (RANDOM) | :TQ10000 |     1 |            |          |  Q1,
00 | P->S | QC (RAND)  |

|   4 |     SORT AGGREGATE     |          |     1 |            |          |  Q1,
00 | PCWP |            |

|   5 |      PX BLOCK ITERATOR |          |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWC |            |

|   6 |       TABLE ACCESS FULL| T1       |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWP |            |

--------------------------------------------------------------------------------
------------------------


Note
-----
   - dynamic sampling used for this statement (level=2)
   - Degree of Parallelism is 60 because of hint


Statistics
----------------------------------------------------------
        430  recursive calls
          0  db block gets
     281608  consistent gets
     158184  physical reads
       3328  redo size
        425  bytes sent via SQL*Net to client
        419  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
         21  sorts (memory)
          0  sorts (disk)
          1  rows processed

在执行时查询并行子进程的是否只在rac1上运行

SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like ('PX%') ORDER BY 1;
   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1         29 PX Deq: Execution Msg                                                    43  268566527          1 1113052640          0
         1         33 PX Deq: Execute Reply                                                 60924        200          1          0          0
         1        104 PX Deq: Execution Msg                                                    51  268566527          1 1113063216          0
         1        103 PX Deq: Execution Msg                                                    48  268566527          1 1011409820          0
         1        101 PX Deq: Execution Msg                                                    53  268566527          1 1113042688          0
         1        100 PX Deq: Execution Msg                                                    53  268566527          1 1011414604          0
         1         99 PX Deq: Execution Msg                                                    54  268566527          1 1113050660          0
         1         91 PX Deq: Execution Msg                                                    59  268566527          1 1113054620          0
         1         90 PX Deq: Execution Msg                                                    47  268566527          1 1011408860          0
         1         88 PX Deq: Execution Msg                                                    60  268566527          1 1113043256          0
         1         87 PX Deq: Execution Msg                                                    45  268566527          1 1113046760          0
         1         86 PX Deq: Execution Msg                                                    52  268566527          1 1113065936          0
         1         85 PX Deq: Execution Msg                                                    45  268566527          1 1113062708          0
         1         84 PX Deq: Execution Msg                                                    59  268566527          1 1011409340          0
         1         83 PX Deq: Execution Msg                                                    45  268566527          1 1113043764          0
         1         82 PX Deq: Execution Msg                                                    46  268566527          1 1113059480          0
         1         81 PX Deq: Execution Msg                                                    52  268566527          1 1113064800          0
         1         80 PX Deq: Execution Msg                                                    43  268566527          1 1113066504          0
         1         76 PX Deq: Execution Msg                                                    61  268566527          1 1113056540          0
         1         69 PX Deq: Execution Msg                                                    48  268566527          1 1113067012          0
         1         68 PX Deq: Execution Msg                                                    48  268566527          1 1113049700          0
         1         66 PX Deq: Execution Msg                                                    61  268566527          1 1011415624          0
         1         64 PX Deq: Execution Msg                                                     2  268566527          1 1113068028         -1
         1         62 PX Deq: Execution Msg                                                    39  268566527          1 1113067520          0
         1         59 PX Deq: Execution Msg                                                    49  268566527          1 1113044840          0
         1         58 PX Deq: Execution Msg                                                    47  268566527          1 1113048740          0
         1         57 PX Deq: Execution Msg                                                    50  268566527          1 1113064232          0
         1         54 PX Deq: Execute Reply                                                 11610        200          1          0          0
         1         53 PX Deq: Execution Msg                                                    52  268566527          1 1113065368          0
         1         43 PX Deq: Execution Msg                                                    42  268566527          1 1113047780          0
         2         80 PX Deq: Execution Msg                                                   133  268566527          2 1112541100          0
         2         83 PX Deq: Execution Msg                                                   119  268566527          2 1112529160          0
         2         78 PX Deq: Execution Msg                                                   107  268566527          2 1112534620          0
         2         77 PX Deq: Execution Msg                                                   144  268566527          2 1112535100          0
         2         76 PX Deq: Execution Msg                                                   146  268566527          2 1112540140          0
         2         74 PX Deq: Execution Msg                                                   118  268566527          2 1112530660          0
         2         73 PX Deq: Execution Msg                                                   150  268566527          2 1112536660          0
         2         72 PX Deq: Execution Msg                                                   125  268566527          2 1112531140          0
         2         71 PX Deq: Execution Msg                                                   157  268566527          2 1112533660          0
         2         70 PX Deq: Execution Msg                                                   146  268566527          2 1112530180          0
         2         69 PX Deq: Execution Msg                                                   135  268566527          2 1112532640          0
         2         67 PX Deq: Execution Msg                                                   128  268566527          2 1112556120          0
         2         66 PX Deq: Execution Msg                                                   135  268566527          2 1112532100          0
         2         65 PX Deq: Execution Msg                                                   124  268566527          2 1112555640          0
         2         63 PX Deq: Execution Msg                                                   126  268566527          2 1112528620          0
         2         62 PX Deq: Execution Msg                                                   183  268566527          2 1112537140          0
         2         60 PX Deq: Execution Msg                                                   182  268566527          2 1112541580          0
         2         59 PX Deq: Execution Msg                                                   103  268566527          2 1112535580          0
         2         58 PX Deq: Execution Msg                                                   160  268566527          2 1112539600          0
         2         57 PX Deq: Execution Msg                                                   164  268566527          2 1112538580          0
         2         56 PX Deq: Execution Msg                                                   124  268566527          2 1112527528          0
         2         53 PX Deq: Execution Msg                                                   145  268566527          2 1112539060          0
         2         49 PX Deq: Execution Msg                                                   140  268566527          2 1112538100          0
         2         37 PX Deq: Execution Msg                                                   112  268566527          2 1112537620          0
         2         36 PX Deq: Execution Msg                                                   153  268566527          1 1112536120          0
         2         34 PX Deq: Execution Msg                                                    14  268566527          2 1112531620         -1
         2         81 PX Deq: Execution Msg                                                   157  268566527          2 1112533180          0
         2         79 PX Deq: Execution Msg                                                   128  268566527          2 1112557244          0

58 rows selected.

从上面的信息可以看到通过通用服务名rac虽然连接到的实例是rac1,在执行并行查询时并行子进程在实例rac1与rac2上运行,并不是只在rac1实例上运行。

如果你想限制你的查询只在rac1实例上执行,那么执行
alter session set parallel_instance_group=rac1命令,这将限制并行子进程只在指定服务名所相关的实例上运行,比如rac1。

SQL> alter session set parallel_instance_group='rac1';

Session altered.

SQL> show parameter parallel_instance_group

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string      rac1

SQL> select /*+ parallel(t1,60) */ count(*) from t1;

  COUNT(*)
----------
  11121536

Elapsed: 00:00:41.25

Execution Plan
----------------------------------------------------------
Plan hash value: 3110199320

--------------------------------------------------------------------------------
------------------------

| Id  | Operation              | Name     | Rows  | Cost (%CPU)| Time     |    T
Q  |IN-OUT| PQ Distrib |

--------------------------------------------------------------------------------
------------------------

|   0 | SELECT STATEMENT       |          |     1 |   793   (0)| 00:00:01 |
   |      |            |

|   1 |  SORT AGGREGATE        |          |     1 |            |          |
   |      |            |

|   2 |   PX COORDINATOR       |          |       |            |          |
   |      |            |

|   3 |    PX SEND QC (RANDOM) | :TQ10000 |     1 |            |          |  Q1,
00 | P->S | QC (RAND)  |

|   4 |     SORT AGGREGATE     |          |     1 |            |          |  Q1,
00 | PCWP |            |

|   5 |      PX BLOCK ITERATOR |          |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWC |            |

|   6 |       TABLE ACCESS FULL| T1       |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWP |            |

--------------------------------------------------------------------------------
------------------------


Note
-----
   - dynamic sampling used for this statement (level=2)
   - Degree of Parallelism is 60 because of hint


Statistics
----------------------------------------------------------
        430  recursive calls
          0  db block gets
     281608  consistent gets
     158184  physical reads
       3328  redo size
        425  bytes sent via SQL*Net to client
        419  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
         21  sorts (memory)
          0  sorts (disk)
          1  rows processed

SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like ('PX%') ORDER BY 1;

   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1         43 PX Deq: Execution Msg                                                    61  268566527          2 1113060496          0
         1         53 PX Deq: Execution Msg                                                    71  268566527          2 1011415624          0
         1         54 PX Deq: Parse Reply                                                   28202        200          1          0         -1
         1         55 PX Deq: Execution Msg                                                    64  268566527          1 1011418240          0
         1         57 PX Deq: Execution Msg                                                    88  268566527          1 1113048740          0
         1         58 PX Deq: Execution Msg                                                    53  268566527          1 1113061632          0
         1         62 PX Deq: Execution Msg                                                    66  268566527          3 1011420904          0
         1         64 PX Deq: Execution Msg                                                    58  268566527          1 1011407468          0
         1         66 PX Deq: Execution Msg                                                    75  268566527          2 1113061124          0
         1         67 PX Deq: Execution Msg                                                     2  268566527          1 1113079488         -1
         1         68 PX Deq: Execution Msg                                                    76  268566527          2 1011417732          0
         1         69 PX Deq: Execution Msg                                                    56  268566527          3 1011420424          0
         1         76 PX Deq: Execution Msg                                                    70  268566527          1 1011408860          0
         1         79 PX Deq: Execute Reply                                                   672        200          1          0          0
         1         80 PX Deq: Execution Msg                                                    75  268566527          1 1011419944          0
         1         81 PX Deq: Execution Msg                                                    75  268566527          1 1011409340          0
         1         82 PX Deq: Execution Msg                                                    63  268566527          1 1113054620          0
         1         83 PX Deq: Execution Msg                                                    62  268566527          2 1011407948          0
         1         85 PX Deq: Execution Msg                                                    65  268566527          3 1113049700          0
         1         86 PX Deq: Execution Msg                                                    54  268566527          2 1113047780          0
         1         88 PX Deq: Execution Msg                                                    65  268566527          3 1113059480          0
         1         90 PX Deq: Execution Msg                                                    83  268566527          2 1113049220          0
         1         91 PX Deq: Execution Msg                                                    65  268566527          1 1113052640          0
         1        101 PX Deq: Execution Msg                                                    69  268566527          2 1113053600          0
         1        102 PX Deq: Execution Msg                                                    56  268566527          2 1113056540          0
         1        103 PX Deq: Execution Msg                                                    70  268566527          2 1113044840          0
         1        104 PX Deq: Execution Msg                                                    70  268566527          2 1113046760          0
 
28 rows selected.

可以看到在设置parallel_instance_group=’rac1’后,并行子进程只能在实例rac1上运行了。

3.如果连接的服务名运行在两个实例上,比如:srvctl add service -d rac -s rac -r rac1,rac2那么,并行查询的并行子进程将会运行在两个实例上,不管你所连接的是那个实例。

SQL> conn sys/system@rac as sysdba

SQL> select instance_name from v$instance;

INSTANCE_NAME
----------------
rac2

SQL> show parameter parallel_instance_group

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string
SQL> show parameter instance_groups

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
instance_groups                      string

SQL> show parameter parallel_degree_policy

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_degree_policy               string      auto
SQL> set timing on
SQL> set autotrace on
SQL> select /*+ parallel(t1,60) */ count(*) from t1;

  COUNT(*)
----------
  11121536

Elapsed: 00:00:41.25

Execution Plan
----------------------------------------------------------
Plan hash value: 3110199320

--------------------------------------------------------------------------------
------------------------

| Id  | Operation              | Name     | Rows  | Cost (%CPU)| Time     |    T
Q  |IN-OUT| PQ Distrib |

--------------------------------------------------------------------------------
------------------------

|   0 | SELECT STATEMENT       |          |     1 |   793   (0)| 00:00:01 |
   |      |            |

|   1 |  SORT AGGREGATE        |          |     1 |            |          |
   |      |            |

|   2 |   PX COORDINATOR       |          |       |            |          |
   |      |            |

|   3 |    PX SEND QC (RANDOM) | :TQ10000 |     1 |            |          |  Q1,
00 | P->S | QC (RAND)  |

|   4 |     SORT AGGREGATE     |          |     1 |            |          |  Q1,
00 | PCWP |            |

|   5 |      PX BLOCK ITERATOR |          |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWC |            |

|   6 |       TABLE ACCESS FULL| T1       |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWP |            |

--------------------------------------------------------------------------------
------------------------


Note
-----
   - dynamic sampling used for this statement (level=2)
   - Degree of Parallelism is 60 because of hint


Statistics
----------------------------------------------------------
        430  recursive calls
          0  db block gets
     281608  consistent gets
     158184  physical reads
       3328  redo size
        425  bytes sent via SQL*Net to client
        419  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
         21  sorts (memory)
          0  sorts (disk)
          1  rows processed

SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like ('PX%') ORDER BY 1;
   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1         29 PX Deq: Execution Msg                                                    43  268566527          1 1113052640          0
         1         33 PX Deq: Execute Reply                                                 60924        200          1          0          0
         1        104 PX Deq: Execution Msg                                                    51  268566527          1 1113063216          0
         1        103 PX Deq: Execution Msg                                                    48  268566527          1 1011409820          0
         1        101 PX Deq: Execution Msg                                                    53  268566527          1 1113042688          0
         1        100 PX Deq: Execution Msg                                                    53  268566527          1 1011414604          0
         1         99 PX Deq: Execution Msg                                                    54  268566527          1 1113050660          0
         1         91 PX Deq: Execution Msg                                                    59  268566527          1 1113054620          0
         1         90 PX Deq: Execution Msg                                                    47  268566527          1 1011408860          0
         1         88 PX Deq: Execution Msg                                                    60  268566527          1 1113043256          0
         1         87 PX Deq: Execution Msg                                                    45  268566527          1 1113046760          0
         1         86 PX Deq: Execution Msg                                                    52  268566527          1 1113065936          0
         1         85 PX Deq: Execution Msg                                                    45  268566527          1 1113062708          0
         1         84 PX Deq: Execution Msg                                                    59  268566527          1 1011409340          0
         1         83 PX Deq: Execution Msg                                                    45  268566527          1 1113043764          0
         1         82 PX Deq: Execution Msg                                                    46  268566527          1 1113059480          0
         1         81 PX Deq: Execution Msg                                                    52  268566527          1 1113064800          0
         1         80 PX Deq: Execution Msg                                                    43  268566527          1 1113066504          0
         1         76 PX Deq: Execution Msg                                                    61  268566527          1 1113056540          0
         1         69 PX Deq: Execution Msg                                                    48  268566527          1 1113067012          0
         1         68 PX Deq: Execution Msg                                                    48  268566527          1 1113049700          0
         1         66 PX Deq: Execution Msg                                                    61  268566527          1 1011415624          0
         1         64 PX Deq: Execution Msg                                                     2  268566527          1 1113068028         -1
         1         62 PX Deq: Execution Msg                                                    39  268566527          1 1113067520          0
         1         59 PX Deq: Execution Msg                                                    49  268566527          1 1113044840          0
         1         58 PX Deq: Execution Msg                                                    47  268566527          1 1113048740          0
         1         57 PX Deq: Execution Msg                                                    50  268566527          1 1113064232          0
         1         54 PX Deq: Execute Reply                                                 11610        200          1          0          0
         1         53 PX Deq: Execution Msg                                                    52  268566527          1 1113065368          0
         1         43 PX Deq: Execution Msg                                                    42  268566527          1 1113047780          0
         2         80 PX Deq: Execution Msg                                                   133  268566527          2 1112541100          0
         2         83 PX Deq: Execution Msg                                                   119  268566527          2 1112529160          0
         2         78 PX Deq: Execution Msg                                                   107  268566527          2 1112534620          0
         2         77 PX Deq: Execution Msg                                                   144  268566527          2 1112535100          0
         2         76 PX Deq: Execution Msg                                                   146  268566527          2 1112540140          0
         2         74 PX Deq: Execution Msg                                                   118  268566527          2 1112530660          0
         2         73 PX Deq: Execution Msg                                                   150  268566527          2 1112536660          0
         2         72 PX Deq: Execution Msg                                                   125  268566527          2 1112531140          0
         2         71 PX Deq: Execution Msg                                                   157  268566527          2 1112533660          0
         2         70 PX Deq: Execution Msg                                                   146  268566527          2 1112530180          0
         2         69 PX Deq: Execution Msg                                                   135  268566527          2 1112532640          0
         2         67 PX Deq: Execution Msg                                                   128  268566527          2 1112556120          0
         2         66 PX Deq: Execution Msg                                                   135  268566527          2 1112532100          0
         2         65 PX Deq: Execution Msg                                                   124  268566527          2 1112555640          0
         2         63 PX Deq: Execution Msg                                                   126  268566527          2 1112528620          0
         2         62 PX Deq: Execution Msg                                                   183  268566527          2 1112537140          0
         2         60 PX Deq: Execution Msg                                                   182  268566527          2 1112541580          0
         2         59 PX Deq: Execution Msg                                                   103  268566527          2 1112535580          0
         2         58 PX Deq: Execution Msg                                                   160  268566527          2 1112539600          0
         2         57 PX Deq: Execution Msg                                                   164  268566527          2 1112538580          0
         2         56 PX Deq: Execution Msg                                                   124  268566527          2 1112527528          0
         2         53 PX Deq: Execution Msg                                                   145  268566527          2 1112539060          0
         2         49 PX Deq: Execution Msg                                                   140  268566527          2 1112538100          0
         2         37 PX Deq: Execution Msg                                                   112  268566527          2 1112537620          0
         2         36 PX Deq: Execution Msg                                                   153  268566527          1 1112536120          0
         2         34 PX Deq: Execution Msg                                                    14  268566527          2 1112531620         -1
         2         81 PX Deq: Execution Msg                                                   157  268566527          2 1112533180          0
         2         79 PX Deq: Execution Msg                                                   128  268566527          2 1112557244          0

58 rows selected.

从上面的信息可以看到通过通用服务名rac虽然连接到的实例是rac2,在执行并行查询时并行子进程在实例rac1与rac2上运行,并不是只在rac2实例上运行。

4.如果所连接的实例已经设置了instance_groups,那么也可以设置parallel_instance_group来进行限制,就像oracle 10g rac一样。

实例rac1:

SQL> alter system set instance_groups='rac','rac1' scope=spfile sid='rac1';

System altered.

SQL> shutdown immediate
Database closed.
Database dismounted.
ORACLE instance shut down.
SQL> startup
ORA-32004: obsolete or deprecated parameter(s) specified for RDBMS instance
ORACLE instance started.

Total System Global Area  669581312 bytes
Fixed Size                  1366724 bytes
Variable Size             306185532 bytes
Database Buffers          356515840 bytes
Redo Buffers                5513216 bytes
Database mounted.
Database opened.


SQL> show parameter instance_groups

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
instance_groups                      string      rac, rac1
SQL> show parameter parallel_instance_group

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string

将parallel_instance_group设置为rac,并行子进程可能会在实例rac1与rac2上运行

SQL> alter session set parallel_instance_group='rac'; 

Session altered.

SQL> show parameter parallel_instance_group

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string      rac
SQL> set autotrace on
SQL> select /*+ parallel(t1,60) */ count(*) from t1;

  COUNT(*)
----------
  11121536


Execution Plan
----------------------------------------------------------
Plan hash value: 3110199320

--------------------------------------------------------------------------------
------------------------

| Id  | Operation              | Name     | Rows  | Cost (%CPU)| Time     |    T
Q  |IN-OUT| PQ Distrib |

--------------------------------------------------------------------------------
------------------------

|   0 | SELECT STATEMENT       |          |     1 |   793   (0)| 00:00:01 |
   |      |            |

|   1 |  SORT AGGREGATE        |          |     1 |            |          |
   |      |            |

|   2 |   PX COORDINATOR       |          |       |            |          |
   |      |            |

|   3 |    PX SEND QC (RANDOM) | :TQ10000 |     1 |            |          |  Q1,
00 | P->S | QC (RAND)  |

|   4 |     SORT AGGREGATE     |          |     1 |            |          |  Q1,
00 | PCWP |            |

|   5 |      PX BLOCK ITERATOR |          |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWC |            |

|   6 |       TABLE ACCESS FULL| T1       |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWP |            |

--------------------------------------------------------------------------------
------------------------


Note
-----
   - dynamic sampling used for this statement (level=5)
   - Degree of Parallelism is 60 because of hint


Statistics
----------------------------------------------------------
        250  recursive calls
          4  db block gets
     162870  consistent gets
     158172  physical reads
          0  redo size
        425  bytes sent via SQL*Net to client
        419  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed


SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like ('PX%') ORDER BY 1;
   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1          1 PX Deq: Execute Reply                                                 11283        200          1          0          0
         1         35 PX Deq: Execution Msg                                                    45  268566527          1 1113085912          0
         1         86 PX Deq: Execution Msg                                                    36  268566527          1 1039760268          0
         1         85 PX Deq: Execution Msg                                                    42  268566527          1 1039763628          0
         1         84 PX Deq: Execution Msg                                                    40  268566527          1 1039764108          0
         1         83 PX Deq: Execution Msg                                                    49  268566527          2 1039764588          0
         1         81 PX Deq: Execution Msg                                                    42  268566527          1 1113034840          0
         1         80 PX Deq: Execution Msg                                                    33  268566527          1 1113035320          0
         1         78 PX Deq: Execution Msg                                                    37  268566527          1 1113036280          0
         1         77 PX Deq: Execution Msg                                                    54  268566527          1 1113058080          0
         1         75 PX Deq: Execution Msg                                                     2  268566527          1 1039758828         -1
         1         74 PX Deq: Execution Msg                                                    50  268566527          2 1113088316          0
         1         73 PX Deq: Execution Msg                                                    54  268566527          1 1113037780          0
         1         72 PX Deq: Execution Msg                                                    50  268566527          1 1113062540          0
         1         70 PX Deq: Execution Msg                                                    46  268566527          1 1113063500          0
         1         69 PX Deq: Execution Msg                                                    54  268566527          1 1113038740          0
         1         68 PX Deq: Execution Msg                                                    60  268566527          1 1113060560          0
         1         66 PX Deq: Execution Msg                                                    43  268566527          2 1113061520          0
         1         65 PX Deq: Execution Msg                                                    56  268566527          1 1113039760          0
         1         63 PX Deq: Execution Msg                                                    64  268566527          1 1113040780          0
         1         62 PX Deq: Execution Msg                                                    59  268566527          1 1113040240          0
         1         61 PX Deq: Execution Msg                                                    69  268566527          1 1113059600          0
         1         60 PX Deq: Execution Msg                                                    70  268566527          2 1113057120          0
         1         58 PX Deq: Execution Msg                                                    46  268566527          2 1113041260          0
         1         50 PX Deq: Execute Reply                                                  5402        200          1          0          0
         1         36 PX Deq: Execution Msg                                                    41  268566527          1 1113037300          0
         2         29 PX Deq: Execution Msg                                                   175  268566527          2 1113084304          0
         2         79 PX Deq: Execution Msg                                                    99  268566527          2 1113067788          0
         2         77 PX Deq: Execution Msg                                                   123  268566527          2 1113068868          0
         2         76 PX Deq: Execution Msg                                                   119  268566527          2 1113069348          0
         2         72 PX Deq: Execution Msg                                                   146  268566527          2 1113071268          0
         2         71 PX Deq: Execution Msg                                                   131  268566527          2 1113071868          0
         2         70 PX Deq: Execution Msg                                                   105  268566527          2 1113072348          0
         2         69 PX Deq: Execution Msg                                                   147  268566527          2 1113072828          0
         2         68 PX Deq: Execution Msg                                                   109  268566527          2 1113073308          0
         2         63 PX Deq: Execution Msg                                                   155  268566527          2 1113087304          0
         2         62 PX Deq: Execution Msg                                                   129  268566527          2 1113074268          0
         2         61 PX Deq: Execution Msg                                                   113  268566527          2 1113096428          0
         2         59 PX Deq: Execution Msg                                                   149  268566527          2 1113087784          0
         2         58 PX Deq: Execution Msg                                                   134  268566527          2 1113085264          0
         2         57 PX Deq: Execution Msg                                                   155  268566527          2 1113084784          0
         2         56 PX Deq: Execution Msg                                                   156  268566527          2 1113082384          0
         2         54 PX Deq: Execution Msg                                                   167  268566527          2 1113081784          0
         2         53 PX Deq: Execution Msg                                                   147  268566527          2 1113085864          0
         2         49 PX Deq: Execution Msg                                                   144  268566527          2 1113083344          0
         2         48 PX Deq: Execution Msg                                                   167  268566527          2 1113095304          0
         2         47 PX Deq: Execution Msg                                                   128  268566527          2 1113083824          0
         2         44 PX Deq: Execution Msg                                                    14  268566527          2 1113067308         -1
         2         37 PX Deq: Execution Msg                                                   151  268566527          2 1113086344          0
         2         36 PX Deq: Execution Msg                                                   148  268566527          2 1113082864          0
         2         35 PX Deq: Execution Msg                                                   133  268566527          2 1113094824          0
         2         78 PX Deq: Execution Msg                                                   102  268566527          2 1113068388          0

52 rows selected.

从上面的信息可以看到当instance_groups设置为’rac’,’rac1’,且parallel_instance_group设置为’rac’时,在实例rac1上执行并行查询时并行子进程能在rac1与rac2实例上运行。

将parallel_instance_group设置为rac1时,并行子进程就只能在rac1实例上运行

SQL> alter session set parallel_instance_group='rac1';

Session altered.

SQL> show parameter parallel_instance_group 

NAME                                 TYPE        VALUE
------------------------------------ ----------- ------------------------------
parallel_instance_group              string      rac1

SQL> select /*+ parallel(t1,60) */ count(*) from t1;

  COUNT(*)
----------
  11121536


Execution Plan
----------------------------------------------------------
Plan hash value: 3110199320

--------------------------------------------------------------------------------
------------------------

| Id  | Operation              | Name     | Rows  | Cost (%CPU)| Time     |    T
Q  |IN-OUT| PQ Distrib |

--------------------------------------------------------------------------------
------------------------

|   0 | SELECT STATEMENT       |          |     1 |   793   (0)| 00:00:01 |
   |      |            |

|   1 |  SORT AGGREGATE        |          |     1 |            |          |
   |      |            |

|   2 |   PX COORDINATOR       |          |       |            |          |
   |      |            |

|   3 |    PX SEND QC (RANDOM) | :TQ10000 |     1 |            |          |  Q1,
00 | P->S | QC (RAND)  |

|   4 |     SORT AGGREGATE     |          |     1 |            |          |  Q1,
00 | PCWP |            |

|   5 |      PX BLOCK ITERATOR |          |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWC |            |

|   6 |       TABLE ACCESS FULL| T1       |    10M|   793   (0)| 00:00:01 |  Q1,
00 | PCWP |            |

--------------------------------------------------------------------------------
------------------------


Note
-----
   - dynamic sampling used for this statement (level=5)
   - Degree of Parallelism is 60 because of hint


Statistics
----------------------------------------------------------
        140  recursive calls
          0  db block gets
     161150  consistent gets
     158026  physical reads
          0  redo size
        425  bytes sent via SQL*Net to client
        419  bytes received via SQL*Net from client
          2  SQL*Net roundtrips to/from client
          0  sorts (memory)
          0  sorts (disk)
          1  rows processed

SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like ('PX%') ORDER BY 1;

   INST_ID        SID EVENT                                                                  SEQ#         P1         P2         P3  WAIT_TIME
---------- ---------- ---------------------------------------------------------------- ---------- ---------- ---------- ---------- ----------
         1          1 PX Deq: Execute Reply                                                 12755        200          1          0          0
         1         34 PX Deq: Execution Msg                                                    61  268566527          1 1113057120          0
         1         35 PX Deq: Execution Msg                                                    75  268566527          1 1113075080          0
         1         36 PX Deq: Execution Msg                                                    56  268566527          1 1113058640          0
         1         47 PX Deq: Execution Msg                                                    39  268566527          1 1113071544          0
         1         50 PX Deq: Execute Reply                                                  8426        200          1          0          0
         1         58 PX Deq: Execution Msg                                                    63  268566527          1 1113036280          0
         1         60 PX Deq: Execution Msg                                                    67  268566527          1 1113087836          0
         1         61 PX Deq: Execution Msg                                                    70  268566527          1 1113078440          0
         1         62 PX Deq: Execution Msg                                                    51  268566527          1 1113085912          0
         1         63 PX Deq: Execution Msg                                                    64  268566527          1 1039759788          0
         1         64 PX Deq: Execution Msg                                                    87  268566527          1 1113077960          0
         1         65 PX Deq: Execution Msg                                                    51  268566527          1 1113088316          0
         1         67 PX Deq: Execution Msg                                                    58  268566527          1 1113062540          0
         1         68 PX Deq: Execution Msg                                                    67  268566527          1 1113077000          0
         1         69 PX Deq: Execution Msg                                                    50  268566527          1 1113063500          0
         1         70 PX Deq: Execution Msg                                                    55  268566527          1 1113076520          0
         1         72 PX Deq: Execution Msg                                                    63  268566527          1 1113076040          0
         1         73 PX Deq: Execution Msg                                                    60  268566527          1 1113061520          0
         1         74 PX Deq: Execution Msg                                                    64  268566527          1 1113075560          0
         1         75 PX Deq: Execution Msg                                                    75  268566527          1 1113072052          0
         1         76 PX Deq: Execution Msg                                                    45  268566527          1 1039764108          0
         1         78 PX Deq: Execution Msg                                                    48  268566527          1 1113074060          0
         1         79 PX Deq: Execution Msg                                                    53  268566527          1 1113073520          0
         1         80 PX Deq: Execution Msg                                                    73  268566527          1 1113058080          0
         1         81 PX Deq: Execution Msg                                                    55  268566527          1 1113073040          0
         1         82 PX Deq: Execution Msg                                                    64  268566527          1 1039759308          0
         1         83 PX Deq: Execution Msg                                                    63  268566527          1 1113072560          0
         1         84 PX Deq: Execution Msg                                                    58  268566527          1 1039758348          0
         1         86 PX Deq: Execution Msg                                                    55  268566527          1 1113059600          0
         1         87 PX Deq: Execution Msg                                                    79  268566527          1 1113074540          0
         1         88 PX Deq: Execution Msg                                                    35  268566527          1 1113035320          0
         1         89 PX Deq: Execution Msg                                                    38  268566527          1 1113070976          0
         1         92 PX Deq: Execution Msg                                                    38  268566527          1 1039753980          0
         1         93 PX Deq: Execution Msg                                                    38  268566527          1 1113069840          0
         1         94 PX Deq: Execution Msg                                                    54  268566527          1 1039753500          0
         1         95 PX Deq: Execution Msg                                                    51  268566527          1 1113069332          0
         1         96 PX Deq: Execution Msg                                                    49  268566527          1 1039753020          0
         1         98 PX Deq: Execution Msg                                                     2  268566527          1 1113063980         -1

40 rows selected.

从上面的信息可以看到当instance_groups设置为’rac’,’rac1’,且parallel_instance_group设置为’rac1’时,在实例rac1上执行并行查询时并行子进程只能在rac1上运行。

parallel_instance_group
在Oracle 10g中 parallel_instance_group的参数值必须是instance_groups的参数列表之一。在11g中这个列表已经扩展包含了所有当前被启用的服务。因此,parallel_instance_group在11g中它的值可以在instance_groups的参数值中找到数据库当前已经启用的服务名之一

parallel_force_local
在11gr2中,parallel_force_local控制着Oracle RAC环境中的并行执行。缺省情况下, 并行执行的并行子进程可以在任何RAC节点或所有节点上运行。通过设置parallel_force_lcoal为true,并行子进程将会受限制,因此它们只能在与查询协调者(QC)所在实例上执行。

SQL> alter session set parallel_force_local=true;

Session altered.

SQL> show parameter parallel_force_local

NAME TYPE VALUE
———————————— ———– ——————————
parallel_force_local boolean TRUE

SQL> select /*+ parallel(t1,60) */ count(*) from t1;

COUNT(*)
———-
11121536

Execution Plan
———————————————————-
Plan hash value: 3110199320

——————————————————————————–
————————

| Id | Operation | Name | Rows | Cost (%CPU)| Time | T
Q |IN-OUT| PQ Distrib |

——————————————————————————–
————————

| 0 | SELECT STATEMENT | | 1 | 793 (0)| 00:00:01 |
| | |

| 1 | SORT AGGREGATE | | 1 | | |
| | |

| 2 | PX COORDINATOR | | | | |
| | |

| 3 | PX SEND QC (RANDOM) | :TQ10000 | 1 | | | Q1,
00 | P->S | QC (RAND) |

| 4 | SORT AGGREGATE | | 1 | | | Q1,
00 | PCWP | |

| 5 | PX BLOCK ITERATOR | | 10M| 793 (0)| 00:00:01 | Q1,
00 | PCWC | |

| 6 | TABLE ACCESS FULL| T1 | 10M| 793 (0)| 00:00:01 | Q1,
00 | PCWP | |

——————————————————————————–
————————

Note
—–
– dynamic sampling used for this statement (level=5)
– Degree of Parallelism is 60 because of hint

Statistics
———————————————————-
140 recursive calls
0 db block gets
161150 consistent gets
158026 physical reads
0 redo size
425 bytes sent via SQL*Net to client
419 bytes received via SQL*Net from client
2 SQL*Net roundtrips to/from client
0 sorts (memory)
0 sorts (disk)
1 rows processed

SQL> SELECT inst_id,sid, event, seq#,p1,p2,p3, wait_time FROM gv$session_wait WHERE upper(event) like (‘PX%’) ORDER BY 1;

INST_ID SID EVENT SEQ# P1 P2 P3 WAIT_TIME
———- ———- —————————————————————- ———- ———- ———- ———- ———-
1 1 PX Deq: Execute Reply 12755 200 1 0 0
1 34 PX Deq: Execution Msg 61 268566527 1 1113057120 0
1 35 PX Deq: Execution Msg 75 268566527 1 1113075080 0
1 36 PX Deq: Execution Msg 56 268566527 1 1113058640 0
1 47 PX Deq: Execution Msg 39 268566527 1 1113071544 0
1 50 PX Deq: Execute Reply 8426 200 1 0 0
1 58 PX Deq: Execution Msg 63 268566527 1 1113036280 0
1 60 PX Deq: Execution Msg 67 268566527 1 1113087836 0
1 61 PX Deq: Execution Msg 70 268566527 1 1113078440 0
1 62 PX Deq: Execution Msg 51 268566527 1 1113085912 0
1 63 PX Deq: Execution Msg 64 268566527 1 1039759788 0
1 64 PX Deq: Execution Msg 87 268566527 1 1113077960 0
1 65 PX Deq: Execution Msg 51 268566527 1 1113088316 0
1 67 PX Deq: Execution Msg 58 268566527 1 1113062540 0
1 68 PX Deq: Execution Msg 67 268566527 1 1113077000 0
1 69 PX Deq: Execution Msg 50 268566527 1 1113063500 0
1 70 PX Deq: Execution Msg 55 268566527 1 1113076520 0
1 72 PX Deq: Execution Msg 63 268566527 1 1113076040 0
1 73 PX Deq: Execution Msg 60 268566527 1 1113061520 0
1 74 PX Deq: Execution Msg 64 268566527 1 1113075560 0
1 75 PX Deq: Execution Msg 75 268566527 1 1113072052 0
1 76 PX Deq: Execution Msg 45 268566527 1 1039764108 0
1 78 PX Deq: Execution Msg 48 268566527 1 1113074060 0
1 79 PX Deq: Execution Msg 53 268566527 1 1113073520 0
1 80 PX Deq: Execution Msg 73 268566527 1 1113058080 0
1 81 PX Deq: Execution Msg 55 268566527 1 1113073040 0
1 82 PX Deq: Execution Msg 64 268566527 1 1039759308 0
1 83 PX Deq: Execution Msg 63 268566527 1 1113072560 0
1 84 PX Deq: Execution Msg 58 268566527 1 1039758348 0
1 86 PX Deq: Execution Msg 55 268566527 1 1113059600 0
1 87 PX Deq: Execution Msg 79 268566527 1 1113074540 0
1 88 PX Deq: Execution Msg 35 268566527 1 1113035320 0
1 89 PX Deq: Execution Msg 38 268566527 1 1113070976 0
1 92 PX Deq: Execution Msg 38 268566527 1 1039753980 0
1 93 PX Deq: Execution Msg 38 268566527 1 1113069840 0
1 94 PX Deq: Execution Msg 54 268566527 1 1039753500 0
1 95 PX Deq: Execution Msg 51 268566527 1 1113069332 0
1 96 PX Deq: Execution Msg 49 268566527 1 1039753020 0
1 98 PX Deq: Execution Msg 2 268566527 1 1113063980 -1

使用parallel_force_local要并使用instance_groups与parallel_instance_group参数来进行限制要方便很多。

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