Every persistent object in the Pega Platform database has an associated class ( Rule-Obj-Class rule type). The Pega Platform uses a simple algorithm and information in Data-Admin-DB-Table instances to determine which table contains objects of which classes.
When in memory and on the clipboard, objects are known as instances and have an XML-like structure consisting of property names and text property values. These can be reviewed with the Clipboard tool.
When saved into the database, objects become rows of a table, with columns corresponding to scalar properties.
- Database foundation classes
Some classes are known as foundation classes in the Pega Platform. These classes must stay in the pr4_base table as initially installed, with the Catalog and Schema fields blank. In addition, never change the database table mappings for these classes.
- Hybrid data storage model (pzPVStream BLOB)
Most columns in the database schema correspond to scalar properties of property mode Single Value. The column name is the same as the property name. These columns are known as exposed columns.
- Database table primary key (handle)
The primary key column for almost all Pega Platform database tables is named pzInsKey, which corresponds to the pzInsKey property known as the internal key or handle. This permanent key is generated internally by concatenating other properties in the instance and, for rules, from the date and time the object is first saved. The key uniquely defines an instance.
- Required columns for tables
Every database table that you add to the Pega Platform database must contain these five columns.
- How database tables are identified at run time
When saving or reading an object as a row in the database, the system uses pattern inheritance based on the class name of the object to find a database table.
- Stored procedures
The Pega Platform database uses stored procedures to ensure database integrity and consistency. Stored procedure names begin with the prefix SPPC_.