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10g QMON Architecture及AQ_TM_PROCESSES

在Oracle Database 10g中,如果你注意过,可能你已经发现AQ_TM_PROCESSES参数的设置已经发生了变化。


SQL> show parameter aq

------------------------------------ ----------- ------------------------------
aq_tm_processes integer 0
SQL> select * from v$version;

Oracle Database 10g Enterprise Edition Release - Prod
PL/SQL Release - Production
CORE Production
TNS for Linux: Version - Production
NLSRTL Version - Production


Metalink Note:305662.1 中有这样一段详细描述:

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.


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By eygle on 2008-10-31 14:44 | Comments (0) | Advanced | 2075 |

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