使用直接的方式访问数据中心越来越困难，有时候远程地执升级和安装是惟一可行的方法。
With physical access to data centers getting more and more difficult, doing upgrades and installs remotely is sometimes the only practical option.
缺乏数据库级别的安全模型使得充分利用ZEO存储服务器变得非常困难，因为客户端或多或少地拥有对数据库的自由访问，因此客户端必须受信任。
The lack of a database-level security model makes it difficult to fully leverage ZEO storage servers as clients have more or less unfettered access to the database and must therefore be trusted.
定义和应用业务规则(应该对数据进行定型)仍然非常困难，并且也很难提供虚拟化技术来让数据用户访问此构型。
It's still very difficult to define and apply the business rules that should shape the data and to provide the visualization technology to make that shape accessible to the users of the data.
请考虑在获得对多个数据存储(其中所有数据存储都需要不同的身份验证技术)的访问权限时所存在的困难。
Consider the difficulty in gaining access to multiple data stores, all of which require different authentication techniques.
然而，通过访问者添加新数据类型(类)较为困难，因为访问者模式要求所有具体类型都具有一个visit方法。
Adding new data types (classes) with visitors is difficult, however, as the visitor pattern requires a visit method for all concrete types.
相同的数据的冗余副本，然而，会浪费存储空间，减缓网络性能，使访问或恢复关键任务数据更加困难。
Redundant copies of the same data, however, can waste storage space, slow down network performance and make accessing or restoring mission critical data more difficult.
当数据具有关系结构时，其在数据访问、存储和可扩展性方面会非常高效，但编写高效的、可维护的代码则变得非常困难。
When data has a relational structure, data access, storage, and scalability are very efficient, but writing efficient and maintainable code becomes more difficult.
当数据具有关系结构时，其在数据访问、存储和可扩展性方面会非常高效，但编写高效的、可维护的代码则变得非常困难。
When data has a relational structure, data access, storage, and scalability are very efficient, but writing efficient and maintainable code becomes more difficult.
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