此外，在Sessionbean中执行所有CMP操作使得Web应用程序无需知道数据库访问层的任何实现细节。
Also, performing all CMP operations in a session bean shields the Web application from having to know any of the implementation details of the database access layer.
系统使用五层体系结构，分别为：用户交互层，系统编程接口层，挖掘核心服务层，数据库访问层，数据库。
The system structure is a multilayer system structure with five layers. They are user interactive layer, system program interface layer, mining core service layer, data access layer, database layer.
这里的模型可以看作数据访问层，应用程序在这里与其他数据库和信息源交互。
The Model can be seen as the data-access layer, where the application interacts with any databases and information sources.
如果对源数据库的访问不可靠，在缓存层争取弹性可能会提高读密集型应用程序的总体稳定性。
If access to the source database is unreliable, striving for resiliency in the cache layer might improve overall stability for read-intensive applications.
最后，数据访问层是持久化的数据存储，比如数据库或文件存储。
Finally, the data access layer is a persistent data store, such as a database or file storage.
数据访问层提供了一种语义数据存储、一个用户个人文件以及规则数据库。
The data access layer provides a semantic data store, a user profile, and the rules database.
数据服务器层是数据网格的组成部分，通过在内存中缓存对象来缓冲数据库访问，以实现更高的性能。
Data Server tier, part of data Grid, buffers database access by caching objects in-memory for higher performance.
为了配置数据层以及应用程序用于访问数据库的工具。
To configure the data layer and the tools that access the database for your application.
通过在FrameworkManager中描述一个元数据层，来自大部分数据库和其他来源(比如web服务)的数据在Cognos报告中都可以被访问。
Data from most databases and other sources, such as Web services for example, can be accessed in Cognos reports by describing a metadata layer in Framework Manager.
如图16所示，此对象将必要的数据传递给BLL，后者随后请求数据访问层将数据保存到MySQL数据库。
As illustrated in Figure 16, this object passes the necessary data to the BLL, which then requests the data Access Layer to save the data to MySQL database.
在场景中，要求通过一种3层设计，使RIA能够访问数据库，同时又无需传输任何敏感数据。
The scenario considers a RIA accessing a database without transferring any sensitive data by using a 3-tier design.
通过允许Web服务器直接访问包含动态内容的其他数据资源(比如数据库)，2层Web架构可以满足这些需求。
The 2-tier Web architecture addressed these requirements by giving Web servers direct access to other data resources (such as a database) that provide dynamic content.
它是一个分布式的内存缓存系统，Facebook(包含其他很多网站)用它作为Web服务器和MySQL服务器之间的缓存层(因为数据库访问相对比较慢)。
It's a distributed memory caching system which Facebook (and a ton of other sites) use as a caching layer between the web servers and MySQL servers (since database access is relatively slow).
应用程序的主要层是数据库、持久性框架、数据库访问对象和用户界面(UI)控制器及视图层。
The main layers of the application are a database, a persistence framework, a database access object, and user interface (UI) controller and view layers.
PHP的数据库访问是使用PEAR：DB完成的，这是一个方便的数据库抽象层，不管数据库是如何实现的，它都可以使用相同的数据库访问代码。
PHP's database accesses are done using PEAR: : DB, a handy database abstraction layer that allows the same database-access code to be used regardless of what database is implemented.
数据库经常由组件和对象访问，而组件和对象又由另一层代码调用，这一层通常就是所谓的中间层。
The database is often accessed by components or objects that execute on the server and are called by other layers of code, often referred to as the middle tier.
业务层和数据库没有任何通讯-这些有数据访问层处理。
The Business Layer does not have any direct communication with the database - this is all handled by the Data Access Layer.
在两层的客户端应用模型中，人们甚至会直接从事件处理器中访问数据库。
In 2-tier Client application models people were even accessing the database directly from the event-handlers.
例如，在Cognos报告中，可以通过在FrameworkManager中描述一个元数据层，来访问大多数数据库和其他数据源，例如Web服务中的数据。
Data from most databases and other sources, like Web services, can be accessed, for example, in Cognos reports by describing a metadata layer in Framework Manager.
该示例应用程序通过服务层从两个层访问数据库，以演示如何在这两个层中使用Spring。
The sample application accesses the database through the service layer from both tiers to demonstrate how we use Spring in both of them.
通常，您将在Web或EJB应用程序层中访问数据库数据，但不会同时在这两个层中进行访问。
Typically you would access database data in either the Web or EJB application tiers, but not both.
如果产品类型层次结构相对简单(只有3或4层)，那么数据库访问就会简单一些。
If your product type hierarchy is relatively flat (only three or four levels deep), then there is less of a concern with database access.
PDO并不是类似于PearDB的数据库抽象层，而更像一种采用了统一api(应用编程接口)的数据访问层。
PDO is not an abstraction layer like PearDB. PDO is a more like a data access layer which USES a unified API (Application Programming Interface).
一旦数据库发生变更，用户只需重新生成数据访问层即可。
Once database schema is changed, user only re-generates the data access layer easily.
数据访问层提供优化的数据访问方法，与课件数据库进行连接；
The data access level provides optimized data access methods and carries on the connection with the courseware database.
商业服务层中，服务器端执行的ASP服务程序是通过ADO来实现对数据库的访问。
In the Business service, ASP service program running in server access database by using ADO.
PDO提供了一个数据访问抽象层，这就意味着，不管你使用的是哪种数据库，你都可以用同样的函数去进行查询的获取数据。
PDO provides a data-access abstraction layer, which means that, regardless of which database you're using, you use the same functions to issue queries and fetch data.
如果改变了数据库结构，就需要相应地改变数据访问层、视图层等。
If you change the database structure, you need to accordingly change the data access layer, view layer.
如果改变了数据库结构，就需要相应地改变数据访问层、视图层等。
If you change the database structure, you need to accordingly change the data access layer, view layer.
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