The Pega Platform relational database holds the rules, data instances, work items, history, and other concrete objects from the internal classes of your Pega Platform system. External classes, by definition, correspond to tables in other databases and are not part of the Pega Platform database.
Tables and views in the Pega Platform database become visible when you
use Database Table instances ( Data-Admin-DB-Table ). For example, the
Data-Admin-Operator-ID class defines users and their organization. The
property pyUserName in that class can contain as its value a text string
for a user name. When your system is first installed, instances of the
Data-Admin-Operator-ID class are saved as rows in the
pr_operators database table, which are identified in the database table
instance named Data-Admin-Operator-ID. The column named
pyUserName contains the text string for the name.
Your applications can use report definition rules or the Obj-Browse method to generate SQL statements that search the database and generate reports. For security and performance reasons, the Pega Platform uses prepared statements to access the Pega Platform database. The SELECT, WHEN, and other parts of the SQL statements are parameters of the prepared statements.
For information about dividing large work tables and indexes into smaller and more manageable tablespaces, see the Pega Community article PegaRULES table partitioning.
- Understanding the unique features of the Pega Platform database
The Pega Platform database and the tables within it are structured in a unique way. By understanding how the database is structured, you are better able to support system upgrades and to be responsive to changes in data utilization.
- Working with class groups
A class group data instance unifies a set of classes in the PegaRULES database that share a common name structure and common key structure. A class group causes all instances of these classes to be stored in one database table. As a result, processing can later convert an instance of any member class from its current class to another class within the class group, without affecting the key structure or changing the database table that holds the instance.
- Planning for property optimization
The values of all aggregate properties and all Single Value properties are stored in a BLOB column (the Storage Stream), usually in a compressed form. These properties cannot be retrieved for reports and can slow retrieval and processing in other operations. You can improve reporting and searching performance by optimizing, that is exposing, Single Value properties as distinct columns; however, doing so might slow insert and update operations, depending on your hardware and software.
- Administering your database
Monitor your database so that it robustly supports a production-level application. Modify your database to support quick data retrieval and to increase column lengths as your initial requirements change.
- Temporary files
Temporary files are created in temporary files directories on the Pega Platform server to temporarily contain information that is required during installation or browsing.