DB2 Data Links Manager Quick Beginnings

The DATALINK data type

Data Links technology includes the DATALINK data type, implemented as an SQL data type in DB2 Universal Database, which references an object stored external to a database.

You use the DATALINK data type, just like any other SQL data type, to define columns in tables. In NTFS and JFS environments the DATALINK values encode the name of a Data Links server containing the file and the filename in terms of a Uniform Resource Locator (URL). The DATALINK value is robust in terms of integrity, access control, and recovery: DB2 treats a DATALINK value as if the object were stored in the database. You register a set of known Data Links servers. The only Data Links server names that you can specify in a DATALINK value are those which have been registered to a DB2 database.

In DCE-DFS environments, the Data Links Manager is registered for the entire cell, and linked files are referred to in terms of a URL with scheme, dfs and the DFS pathname of the file.

Even though the DATALINK value represents an object that is stored outside the database system, you can use SQL queries to search parametric data to obtain the file name that corresponds to the query result. You can create indexes on files containing video, images, text, or other media formats, and store those attributes in tables along with the DATALINK value. With a central repository of files on a file server and DATALINK data types in a database, you can obtain answers to questions like, "What do I have?" and "Help me find what I'm looking for".

Examples of applications that can use the DATALINK data type are:

• Medical applications, in which X-rays are stored on the file server and the attributes are stored in a database.
• Entertainment industry applications that perform asset management of video clips. The video clips are stored on a file server, but attributes about the clips are stored in a database. Access control is required for accessing the video clips based on database privileges of accessing the meta-information.
• World Wide Web applications that manage millions of files and allow access control based on database privileges.
• Financial applications, which require distributed capture of check images and a central location for those images.
• CAD and CAM applications, where the engineering drawings are kept as files, and the attributes are stored in the database. Queries are run against the drawing attributes.