oracle 之 内存—鞭辟近里(四)

oracle 之 内存—鞭辟近里(四)

今天是2013-07-11日,首先我非常感谢我的哥们也是我的网友杨工,非常感谢他能在大数据库内帮我执行一下我所需要的信息。就是他说的网络真是一个互助友爱的平台。

前面,我学习 pga内存的结构concept以及常用的动态查看pga的分配使用情况。现在我在学习一下怎么启动pga管理。
如果启动一个自动管理的pga,需要配置二个参数,一个是pga_aggregate_target,一个是workarea_size_policy,这些参数在前面我学习了,但是如何设置pga_aggregate_target这个参数在刚刚创建新的库的时候是可以通过前面oracle建议的步骤进行设定的,
但是运行一段时间后我们还是需要重新设置该参数:
1)pga advice view;
在查看该相关视图需要确保statistics_level运行在typical或是all状态,不然就没法查看建议值了。

Setting the STATISTICS_LEVEL parameter toBASIC disables the collection of many of the important statistics required by Oracle Database features and functionality, including:

  • Automatic Workload Repository (AWR) Snapshots

  • Automatic Database Diagnostic Monitor (ADDM)

  • All server-generated alerts

  • Automatic SGA Memory Management

  • Automatic optimizer statistics collection

  • Object level statistics

  • End to End Application Tracing (V$CLIENT_STATS)

  • Database time distribution statistics (V$SESS_TIME_MODEL andV$SYS_TIME_MODEL)

  • Service level statistics

  • Buffer cache advisory

  • MTTR advisory

  • Shared pool sizing advisory

  • Segment level statistics

  • PGA Target advisory

  • Timed statistics

  • Monitoring of statistics
    eg:
    SYS@orcl#SHOW PARAMETER STATISTICS_LEVEL

NAME                                 TYPE                   VALUE
------------------------------------ ---------------------- ------------------------------
statistics_level                     string                 TYPICAL
SYS@orcl#R
  1* select PGA_TARGET_FOR_ESTIMATe/1024/1024 PGA_TARGET_FOR_ESTe,PGA_TARGET_FACTOR,ADVICE_STATUS,BYTES_PROCESSED/1024/1024 BYTES_PROCESSED,ESTD_TIME,ESTD_EXTRA_BYTES_RW/1024/1024 ESTD_EXTRA_BYTES_RW,ESTD_PGA_CACHE_HIT_PERCENTAGE,ESTD_OVERALLOC_COUNT from v$pga_target_advice
PGA_TARGET_FOR_ESTE PGA_TARGET_FACTOR ADVICE BYTES_PROCESSED  ESTD_TIME ESTD_EXTRA_BYTES_RW ESTD_PGA_CACHE_HIT_PERCENTAGE ESTD_OVERALLOC_COUNT
------------------- ----------------- ------ --------------- ---------- ------------------- ----------------------------- --------------------
                 32              .125 ON          1018.20703      22139          289.753906                            78                   41
                 64               .25 ON          1018.20703      22139          289.753906                            78                   41
                128                .5 ON          1018.20703      17235                   0                           100                    0
                192               .75 ON          1018.20703      17235                   0                           100                    0
                256                 1 ON          1018.20703      17235                   0                           100                    0
         307.199219               1.2 ON          1018.20703      17235                   0                           100                    0
         358.399414               1.4 ON          1018.20703      17235                   0                           100                    0
         409.599609               1.6 ON          1018.20703      17235                   0                           100                    0
         460.799805               1.8 ON          1018.20703      17235                   0                           100                    0
                512                 2 ON          1018.20703      17235                   0                           100                    0
                768                 3 ON          1018.20703      17235                   0                           100                    0
PGA_TARGET_FOR_ESTE PGA_TARGET_FACTOR ADVICE BYTES_PROCESSED  ESTD_TIME ESTD_EXTRA_BYTES_RW ESTD_PGA_CACHE_HIT_PERCENTAGE ESTD_OVERALLOC_COUNT
------------------- ----------------- ------ --------------- ---------- ------------------- ----------------------------- --------------------
               1024                 4 ON          1018.20703      17235                   0                           100                    0
               1536                 6 ON          1018.20703      17235                   0                           100                    0
               2048                 8 ON          1018.20703      17235                   0                           100                    0
已选择14行。
可以看到我们应该设置pga_aggregate_target大小为128M。
如果我把statistics_level参数设置为basic,那么oracle就会取消相关的功能。
另外还有v$pga_target_advice_histogram;这个视图。
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