READ_ONLY_OPEN_DELAYED

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于 2021-07-14 13:39:02 发布

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分类专栏： Oracle 文章标签： mysql

本文链接：https://blog.youkuaiyun.com/linsuhangoracle/article/details/118725660

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了解如何通过READ_ONLY_OPEN_DELAYED参数调整，让只读表空间在实际需求时才访问数据，避免数据库打开时的延迟。特别适用于大量存储于慢速设备的读-only数据，设置为true可提升数据库打开速度。

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READ_ONLY_OPEN_DELAYED determines when datafiles in read-only tablespaces are accessed.

true: The datafiles are accessed for the first time only when an attempt is made to read data stored within them.
false(default): The datafiles are accessed at database open time.

You can use this parameter to speed up some operations (primarily opening the database) for very large databases when substantial portions of the database are stored in read-only tablespaces.
Consider setting this parameter to true for such databases, especially if portions of the read-only data are stored on slow-access devices or hierarchical storage.

对于READ ONLY表空间不会在数据库OPEN时进行访问，而是OPEN后用时再访问
对于一些READ ONLY表空间可能数据文件存于slow access devices or hierarchical storage中，设置为true可以加快open速度
另外如果READ ONLY的数据文件不存在(如放在NFS未挂载等)不会影响数据库启动到open