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【等待时间】asynch descriptor resize

原创 Linux操作系统 作者:renjixinchina 时间:2013-10-08 15:40:04 0 删除 编辑
Wait event 'asynch descriptor resize' is waited for when the number of asynchronous descriptors reserved inside the OS kernel is being re-adjusted.

When the number of asynchronous I/O's submitted by a process has to be dynamically increased, the unix kernel is signalled to make the changes and the process will wait on 'asynch descriptor resize' . Many Unix Kernels (for example: Linux kernel) do not allow the limit to be increased when there are outstanding I/O's; all outstanding I/O's must be resolved before the limit is increased. This means that all sessions doing asynchronous I/O will wait at this time. The event is shown when the kernel wants to increase the limit and is waiting for all the outstanding I/O's to be resolved so that the increase can be implemented. 

If you see this wait event often, it might be a good idea to install the fix for (unpublished) Bug: 9829397 ASYNC DESCRIPTOR RESIZE which adjusts the frequency of resize calls.  
The fix for (unpublished) Bug 9829397 is included in 11.2.0.2.5, 11.2.0.3 and Oracle 12g

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