What is the common storage structure for custom tables in SAP?

The common storage structure for custom tables in SAP is transparent tables. Transparent tables are designed to store application data in a database in a straightforward manner. Each transparent table corresponds directly to a table in the database, allowing for efficient data storage and retrieval.

Unlike cluster tables and pool tables, which are used for specific data storage strategies that combine data from multiple logical entities, transparent tables provide a one-to-one mapping with the underlying database tables. This structure results in straightforward data modeling and simplifies the development process, allowing developers to create custom tables that can be easily managed and accessed.

System tables, on the other hand, are maintained by the SAP system and are not typically used for custom application data. Transparent tables, therefore, represent the standard approach for developers wanting to create custom data structures in SAP applications.