在许多情况下，作为在女孩的青春期之前，或在怀孕期间，哺乳或绝经期，这是正常的，也是所谓的生理闭经。

In many cases, as in girls before puberty, or during pregnancy, breastfeeding or the menopause, this is normal and is called physiological amenorrhoea.

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实时数据库系统的事务调度一般只考虑事务的截止期，但是，在很多情况下，它还与数据截止期直接相关。

Generally the deadline of transaction is only considered in dealing with real-time transaction scheduling, but in many cases, scheduling method is directly related with data deadline.

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