The effect of this is that if an event handler implements a request-response operation, then only one instance of such an event handler may be active at any point in time.

此规定的结果是，如果某个事件处理程序实现了一个请求-响应操作，则在任何时间点，只能有一个此类事件处理程序的实例处于活动状态。

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Therefore, WS-BPEL claims that only one request-response operation per process instance may be active at any given time for each port type, operation, correlation set, and partner link.

因此，WS-BPEL 要求，在任何给定时间，对于每个端口类型、操作、相关集和伙伴链接，每个流程实例只能有一个请求-响应操作。

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Only one defragment operation is allowed on a partition at a time.

在一个分区上，仅允许同时进行一个碎片整理操作。

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The UN's peacekeeping mission has been in DR Congo for more than a decade and was at one time the biggest peacekeeping operation in the world.

BBC: UN combat force to target DR Congo rebels

As for the little Syrian girl who has survived a war and now open-heart surgery, she will need one more operation in about a year's time as her body grows.

CNN: Taking heart amid Syria's carnage

Earlier this year, BBC Newsline carried out a series of reports into a USPCA operation which been tracking one gang for some time.

BBC: Badger