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  • 并行进程

    SQL> show parameter parallel_min

     

    NAME                     TYPE    VALUE

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

    parallel_min_percent             integer 0

     

    SQL> show parameter parallel_max

     

    NAME                     TYPE    VALUE

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

    parallel_max_servers             integer 960

     

    SQL> select * from v$px_process_sysstat;

     

    STATISTIC                             VALUE

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

    Servers In Use                                0

    Servers Available                            64

    Servers Started                             308

    Servers Shutdown                            244

    Servers Highwater                            64

    Servers Cleaned Up                            0

    Server Sessions                          226823

    Memory Chunks Allocated                         105

    Memory Chunks Freed                          87

    Memory Chunks Current                            18

    Memory Chunks HWM                            23

     

    STATISTIC                             VALUE

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

    Buffers Allocated                       1771708

    Buffers Freed                           1771708

    Buffers Current                               0

    Buffers HWM                            1566

     

    15 rows selected.

     

    Servers In Use: 正在使用的并行进程的数量

     

    Servers Available:可用的并行进程的数量

     

    执行SQL:

    SQL> select /*+ parallel(a 8)*/ count(*) from T_PM_ACCT_DTL a;

    对应8个进程

    祖宗进程为384

    那么加上group by order by呢?

    SQL> select /*+ parallel(a 8)*/ count(*) from T_PM_ACCT_DTL a group by a.data_date order by a.data_date;

    可以看到已经使用了16个

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  • 原文地址:https://www.cnblogs.com/hzcya1995/p/13352442.html
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