10g QMON Architecture及AQ_TM_PROCESSES

在Oracle Database 10g中，如果你注意過，可能你已經發現AQ_TM_PROCESSES參數的設置已經發生了變化。

缺省的這個參數被設置為0，Oracle啟動了自動調整：SQL> show parameter aq

NAME TYPE VALUE

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

aq_tm_processes integer 0

SQL> select * from v$version;

BANNER

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

Oracle Database 10g Enterprise Edition Release 10.2.0.1.0 - Prod

PL/SQL Release 10.2.0.1.0 - Production

CORE 10.2.0.1.0 Production

TNS for Linux: Version 10.2.0.1.0 - Production

NLSRTL Version 10.2.0.1.0 - Production

在某些版本升級之后，你可能發現告警日志中存在以下警告：

WARNING:AQ_TM_PROCESSES is set to 0

Metalink Note:305662.1 中有這樣一段詳細描述:Beginning with release 10.1, the architecture of the QMON processes has been changed to an automatically controlled coordinator slave architecture. The Queue Monitor Coordinator, ora_qmnc_, dynamically spawns slaves named, ora_qXXX_, depending on the system load up to a maximum of 10 per instance.

For version 10.1 onwards it is no longer necessary to set AQ_TM_PROCESSES when Oracle Streams AQ or Streams is used. However, if you do specify a value, then that value is taken into account but the number of processes can still be auto-tuned and so the number of running qXXX processes can be different from what was specified by AQ_TM_PROCESSES. If AQ_TM_PROCESSES is not specified in versions 10.1 and above, QMNC only runs when you have AQ objects in your database.

If should be noted that if AQ_TM_PROCESSES is explicitly specified then the process(es) started will only maintain persistent messages. For example if aq_tm_processes=1 then at least one queue monitor slave process will be dedicated to maintaining persistent messages. Other process can still be automatically started to maintain buffered messages. If you explicitly set aq_tm_processes = 10 then there will be no processes available to maintain buffered messages. This should be borne in mind on 10g systems which use Streams replication and from 10.2 onwards user enqueued buffered messages.

不過最近發現在10g中，自動的高級隊列調度會存在問題，QMNC的動態協同存在問題。這段文字收次備忘。

By eygle on 2008-10-31 14:44 |

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