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  • 更改并行度会清空执行计划缓存

    早上下面报告报表数据库反应很慢,远程桌面发现大查询过后,cpu不怎么动,于是我试着把并行度从0改成了32,恢复正常。
    按道理根据我的服务器配置并行度为0跟32是一样的效果,为什么会恢复正常呢?
     
    以下是群里继伟大神给的答案:
    从0改成32后你的执行计划缓存会被清空,从而重新生成执行计划.你不能动是应该发生了参数嗅探致使低效
    ,从0变成32也好,变成1也好都会有一定效果.但过段时间问题有可能又会出现.
     
    从错误日志里我也找到了答案:
    xp_readerrorlog:
    Configuration option 'max degree of parallelism' changed from 0 to 32. Run the RECONFIGURE statement to install.
    SQL Server has encountered 1 occurrence(s) of cachestore flush for the 'Object Plans' cachestore (part of plan cache) due to some database maintenance or reconfigure operations.
    SQL Server has encountered 1 occurrence(s) of cachestore flush for the 'SQL Plans' cachestore (part of plan cache) due to some database maintenance or reconfigure operations.
    SQL Server has encountered 1 occurrence(s) of cachestore flush for the 'Bound Trees' cachestore (part of plan cache) due to some database maintenance or reconfigure operations.
     
    接下去就是SQL优化的问题了。
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  • 原文地址:https://www.cnblogs.com/ajiangg/p/3644735.html
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