Progress
DataServer
for ORACLE Guide


The Schema Holder

The schema holder contains information about the data definitions for one or more ORACLE databases, or from any other data manager supported by the Progress DataServer architecture. The schema of a database is a description of its structure, the tables, the fields within the tables, and the indexes. That information in the schema holder is called the schema image. When you use a Progress client with an ORACLE database, the DataServer uses the schema image to translate Progress database requests into a format that can be used to access the data in the ORACLE database.

The schema image contains all the database information for developing a Progress DataServer application, which lets you develop and compile applications for an ORACLE database without being connected to it.

Progress accesses the schema holder only when it compiles procedures and at the beginning of a run-time session for schema caching. Schema caching occurs when data definitions are loaded into memory. Typically, the schema holder is idle during a run-time session after the initial schema caching.

Before a Progress client can access ORACLE data, you must create a schema holder and load the ORACLE database definitions—the schema image—into the schema holder. Then you can use the Data Dictionary to add Progress database features, such as validation expressions or messages.

Figure 1–3 illustrates the schema-loading process.

Figure 1–3: The Schema-loading Process


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