Win9x Support
In addition to improving SQL Server 7.0's upward scalability, Microsoft has also extended the software's reach downward with support for Win9x. This support lets you scale SQL Server applications down into a small branch office environment that consists of only a small group of Win9x systems. To optimize SQL Server 7.0 for the Win9x platform, the software incorporates a smaller footprint than previous versions. Microsoft targeted the minimum working set for SQL Server 7.0 to run in about 4MB of memory.
Unlike with some databases, SQL Server 7.0 under Win9x uses the same source code as the NT version to help maximize compatibility between implementations on the two platforms. As a result, all the SQL statements and data access methods that work with the NT implementation will work with the Win9x implementation. However, you encounter some differences between the two platforms when you run SQL Server 7.0. For example, SQL Server runs as a service under NT and runs as a standard executable under Win9x because Win9x doesn't support services. Likewise, Win9x lacks NT's security model and offers no integrated security support. As a result, Win9x must use SQL Server's built-in security; NT has the option of using SQL Server's integrated security.
SQL Server's Win9x support has led some users to speculate that SQL Server 7.0 will replace Microsoft Access as the desktop database engine. However, considering that Microsoft is currently developing Access 4.0, don't count on the SQL Server engine becoming the new desktop standard anytime soon. However, the SQL Server engine will play a big role in the upcoming version of Access. Access 98 will use both the Jet database engine and a new implementation of the SQL Server engine (code-named Stinger) natively.
Data Warehousing and OLAP
Improved data warehousing support is a major part of SQL Server 7.0. The biggest new data warehousing-related feature is the addition of Microsoft's new online analytical processing (OLAP) server, known as the Microsoft SQL Server OLAP Services. Microsoft SQL Server OLAP Services provides the multidimensional data navigation and query capabilities that decision-support applications need. Microsoft SQL Server OLAP Services supports Multidimensional (MOLAP), Relational (ROLAP) or Hybrid (HOLAP) implementations. Microsoft SQL Server OLAP Services can also integrate with Microsoft Office applications such as Excel Pivot Tables and includes the Object Linking and Embedding Database (OLE DB) for OLAP provider and ActiveX Data Object MultiDimensional (ADOMD) that enable custom access. Screen 5 presents the Microsoft SQL Server OLAP Services.
In addition to supporting OLAP, SQL Server 7.0 supports Distributed Merge Replication so mobile and offline users can work autonomously and then merge their offline information into a central database. Distributed Merge Replication and Win9x support are a potent tag-team that can take SQL Server into the small branch office environment. In this scenario, branch offices can use their local Win9x database during the day and then replicate the day's transactions to a central NT server in the main office overnight. Merge replication can take place using Remote Access Service (RAS) connections or across the Internet.
Data Transformation Services
SQL Server 7.0's new Data Transformation Service (DTS) facilitates transferring data between SQL Server and various other database systems. DTS uses an OLE DB architecture that lets DTS work with relational and non-relational data sources. You can access DTS from its wizard interface or use it procedurally from the Visual Basic Script (VBScript) or Jscript source files that it can generate. The DTS wizard steps you through the process of selecting a source and target data source and the type of conversions that you want to apply to all the data columns. Screen 6 shows the DTS column mappings screen for the authors table in the pubs database.
During the process of selecting the tables and columns, DTS automatically generates a script that an OLE-compliant language such as VB can call to perform the transformation under program control. Screen 7, page 124, shows the script generation window with an example VB script.
DTS is primarily oriented at importing and exporting data to SQL Server, but it also supports 100 percent of both the source and target data sources. As a result, you can use it to transfer data between other external data sources without involving SQL Server. For example, you can use DTS to exchange data directly between an Access database and DB2 or Oracle. Combining this feature with DTS's scripting support lets you use DTS for basic cross-platform data replication.
Data Access Enhancements
To enable database access, SQL Server 7.0 includes several OLE DB providers (e.g., the native OLE DB Provider for SQL Server, OLE DB Provider for ODBC, OLE DB Provider for Oracle, and OLE DB Provider for Jet), ADO 2.0, the ODBC 3.5 driver, and a new version of SQL Distributed Management Objects (DMO). OLE DB and the ADO object model let you perform heterogeneous queries that incorporate data from relational databases (e.g., SQL Server) and non-relational sources (e.g., Excel spreadsheets, indexed sequential access method--ISAM--databases, and mail or document management data sources).
The new SQL-DMO management framework uses a new base object that makes it incompatible with SQL-DMO applications developed using the SQL Server 6.5 object framework. Although Microsoft renamed the SQL Server 7.0 root SQL-DMO object from SQLOLE to SQLDMO, a lot of the framework is the same. I was able to convert most of my existing SQL Server 6.5 SQL-DMO applications in just a few minutes.
Microsoft English Language Query is another data access feature in the new SQL Server release. This feature lets users submit database queries without understanding SQL or other developer-oriented data access methods. With the Microsoft English Language Query, the developer uses the built-in authoring tool to map the database schema to English syntax. The end user can then use the built-up English syntax to perform database queries.
Migration Strategies
SQL Server 7.0 proves that there's no such thing as a free lunch. SQL Server 7.0's changed database structures require you to reload all your existing data into the new SQL Server 7.0 databases. Migrating data is time consuming in the best of circumstances. To help make this job easier, Microsoft provides a Migration Wizard, which can migrate all your existing 6.x database objects to 7.0. The migration process is very flexible (i.e., you can migrate all your databases at once, or you can migrate selected parts).
You must choose between two basic migration strategies. You can perform a side-by-side installation where SQL Server 7.0 runs next to an existing SQL Server 6.x installation on the same computer. Alternatively, you can perform a computer-to-computer installation where SQL Server 7.0 runs on a separate system from SQL Server 6.x. With the side-by-side installation, you can use only one version of SQL Server at a time. Fortunately, SQL Server 7.0 provides a handy Switch feature that lets you quickly switch between versions.
Regardless of which migration strategy you choose, you have two basic paths for migrating your databases: You can use the direct pipeline method or you can use media storage (i.e., tape or network share) to migrate. The direct pipeline method uses a custom OLE DB provider that's quite fast. This method takes data directly from your existing SQL Server 6.5 databases and converts it to SQL Server 7.0 format. Microsoft has reported that the throughput is greater than 1GB per hour and that the company has migrated an 80GB SAP database in about 14.5 hours. The media storage method is available in case you don't have enough disk space to support the direct pipeline method.
Stay Tuned
Touching on all of SQL Server 7.0's new features in one article is a difficult task. Most of the changes will move SQL Server from the role of department server into the role of enterprise database server. The inclusion of the Microsoft SQL Server OLAP Services and support for the Win9x platform will bring about profound changes in the database marketplace. Look for Windows NT Magazine to provide ongoing coverage of SQL Server 7.0's development and features and those of competing database products such as Oracle, DB2, and Sybase. For a list of recent articles on NT-related database products, see "Related Articles in Windows NT Magazine."
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