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• #Wechat windows dev infrastructure database cache manual#

Unfortunately, setting the smallest optimal value for this parameter can only be done using experimentation with the target application.

This can cause very significant performance problems in some cases. This not only results in an increased number of writes to the database files but it also indirectly causes an increased number of reads to those files as well. As the value of this parameter approaches zero, the cache will become more and more aggressive when flushing database pages to disk. It is important that this parameter not be set too low. If circular logging is enabled using JET_paramCircularLog then this parameter will also control the approximate amount of transaction log files that will be retained on disk. The parameter is a threshold in bytes for about how many transaction log files will need to be replayed after a crash. This parameter controls how aggressively database pages are flushed from the database page cache to minimize the amount of time it will take to recover from a crash. Windows Vista and Windows Server 2003: Yes Windows 2000, Windows XP and Windows Server 2003: 512 Windows Vista: As of Windows Vista, the default value of this parameter was changed to clarify this behavior. Note If this parameter is left to its default value, then the maximum size of the cache will be set to the size of physical memory when JetInit is called. This parameter configures the maximum size of the database page cache. Windows XP and later: The cache manager will automatically set its own minimum cache size to avoid deadlocks. This is required to avoid deadlocks caused by an insufficient number of database page cache buffers to perform complex operations like B+ Tree splits. Windows 2000: On Windows 2000, this parameter should be set to a value roughly equal to four times the number of threads that will be inside the ESE API at the same time. The size is in database pages.īy default, the database cache will automatically adjust its size between the limits set by JET_paramCacheSizeMin and JET_paramCacheSizeMax. This parameter configures the minimum size of the database page cache.

#Wechat windows dev infrastructure database cache manual#

This size can be used by the application as an input to drive its manual adjustment of the cache size. When this parameter is read, the actual size of the cache in database pages is returned.

Note The cache size is still subject to the limits imposed by JET_paramCacheSizeMin and JET_paramCacheSizeMax. The cache will then hold its size at that threshold until given a new size or until it is released to choose its own size.

However, if the application sets this parameter to a non-zero value then the cache will adjust itself to that target size (in database pages). If the application sets this parameter to zero, then the cache will tune its own size in this manner. Ordinarily, the cache will automatically tune its size as a function of database and machine activity levels. This parameter can be used to control the size of the database page cache at run time. Windows XP and later: This parameter is obsolete and does not affect the operation of the database engine. This parameter controls the size of an auxiliary part of the database page cache that is used to simulate scatter gather I/O when it is otherwise not available. This topic contains parameters that are used for the database cache. Applies to: Windows | Windows Server Database Cache Parameters