中间件创建一个灵活的系统，在这个系统中，底层的RDBM可以无缝地改变，而且允许用集群替换单一的数据库服务器。
Middleware creates a flexible system where the underlying RDBM may be seamlessly changed, and additionally allows a single database server to be replaced with a cluster of machines.
如果目标是一个文件，那么(单一)源必须也为文件，而源文件的副本使用目标名作为新名，替换任何现有的具有相同名称的文件。
If the target is a file, then the (single) source must also be a file and a copy of the source file is made with the target name as the new name, replacing any existing file of the same name.
在简单的情况下，合并或单一访问点和替换或多或少有些相同。
In the simple case, consolidation or single point of access and substitution become more or less the same.
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