XML schema repository

The XML schema repository (XSR) is a repository for all XML artifacts used to process XML instance documents stored in XML columns. The purpose of the XSR is to support tasks you perform that have a dependency on these XML artifacts.

XML instance documents might contain a reference to a Uniform Resource Identifier (URI) that points to an associated XML schema, DTD or other external entity. This URI is required to process the instance documents. The DB2® database system manages dependencies on such externally referenced XML artifacts with the XSR without requiring changes to the URI location reference.

Without this mechanism to store associated XML schemas, DTDs, or external entities, an external resource may not be accessible when needed by the database, or may be subject to change without also triggering the necessary changes to an already validated and annotated XML document stored within the database. The XSR also removes the additional overhead required to locate external documents, along with the possible performance impact.

Each database contains an XML schema repository that resides in the database catalog and comprises catalog tables, catalog views and some system defined stored procedures to enter data into these catalog tables.