This is the reason why reversing the index when its leading column is fed by a sequence reduces buffer contention , removes the hot block problem and by doing so , reduces the potential for buffer busy waits on a multi - user system 这正是为何当前导（ /起始）列由序列生成时索引的逆序处理可以降低缓存争用，解决热块问题，并且这样做可以在一个多用户系统中减少缓存忙等待的机会。
The separation principle is both extremely powerful and extremely limiting to the advancement of communications technology . with the development of modern communication , some systems will lead to the violation of the separation principle , such as resource constraints , multiuser system or time - varying networks 随着现代通信的发展，独立原则在很多实际场合中，例如资源有限，多用户系统中或网络时变的情况等，都不适用。
The highest isolation level , serializable , guarantees that a transaction will retrieve exactly the same data every time it repeats a read operation , but it does this by performing a level of locking that is likely to impact other users in multi - user systems 最高隔离级别可序列化保证事务在每次重复读取操作时都能准确检索到相同的数据，但需要通过执行某种级别的锁定来完成此操作，而锁定可能会影响多用户系统中的其他用户。
