What is ADO? - ADO and ADO.NET (Page 5 of 12 ) Because Microsoft is pushing its .NET technology very heavily, you might wonder what role ADO has to play in the future. The answer is: a big role. A huge amount has been invested in existing technologies (i.e., those that aren’t .NET). This means that ADO is still important. So if you’re developing applications that use ADO, don’t worry that it will suddenly disappear; Microsoft is committed to supporting it for a very long time. Data Providers and Data Consumers OLE DB introduces two new terms that help to explain how OLE DB and ADO fit together: - A Data Consumer is something that uses (or consumes) data. Strictly speaking, ADO is actually a consumer, because it uses data provided by OLE DB.
- A Data Provider is something that provides data. This isn’t the physical source of the data, but the mechanism that connects you to the physical data store. The provider may get the data directly from the data store, or it may go through another layer (such as ODBC) to get to the data store.
The initial set of OLE DB providers supplied with MDAC 2.8 consists of: - Directory Services, for stored resource data, such as Active Directory. With Windows 2000, the Directory Service allows access to user information and network devices.
- Index Server, for Microsoft Index Server. This will be particularly useful as Web sites grow, because indexed data will be available.
- Site Server Search, for Microsoft Site Server. Again for use with Web sites, especially large, complex sites, where Site Server is used to maintain them.
- Oracle, for Oracle databases. Connecting to Oracle has never been particularly easy with Microsoft products, but a native driver will simplify access to existing Oracle data stores.
- SQL Server, for Microsoft SQL Server, allows access to data stored in SQL Server.
- Data Shape, for hierarchical recordsets. This allows creation of master/detail type recordsets, which allow drilling down into detailed data.
- Persisted Recordset, for locally saved recordsets and recordset marshaling.
- OLAP, for accessing Online Analytical Processing data stores.
- Internet Publishing, for accessing Web resources that support Microsoft FrontPage Server Extensions or Distributed Authoring and Versioning (DAV).
- Remoting Provider, for connecting to data providers on remote machines.
This is just the standard providers supplied by Microsoft; other vendors have created their own. For example, a company called ISG provides an OLE DB provider that allows connections to multiple data stores at the same time. Oracle provides an OLE DB provider, which it claims is better than Microsoft’s Oracle provider, and most other database suppliers have OLE DB providers for their databases. OLE DB also provides a few other services, such as a query processor and a cursor engine, so these can be used at the client. There are two reasons for this. First, it frees the actual provider from providing the service, so the service can be smaller and faster. Second, it makes it available as a client service. This means that cursor handling can be provided locally, which is an important function of disconnected recordsets and Remote Data Services. Another advantage of the Cursor Service is that, as a client-based service, it can provide a more uniform set of features across all providers. Also, the persistence provider (MSPersist)—introduced in ADO 2.5—has the ability to persist a recordset to a stream. Note that Jet and ODBC desktop drivers are not included in ADO versions 2.6 and above. For more details on this, please visit http://support.microsoft.com/ and search for Knowledgebase article number 271908. For the ODBC examples in this book, you must install ADO 2.5 before installing a later version. |
 This is from ADO Programmer's Reference, by Dave Sussman (Apress, ISBN 1590593421). Check it out at your favorite bookstore today. Buy this book now. |
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