Data Area 
The data volumes of a database form the data area. The database system stores the following in the data area:
Application data
Database catalog
The converter saved at the last savepoint
Undo log files
Sequences
Restart information
To improve the performance of large databases, configure data volumes on different hard drives. The general database parameter MaxDataVolumes specifies the maximum number of data volumes you can define for a database.
More information: Database Administration, General Database Parameters
How Does the System Write Data to the Data Area?
The database system uses internal striping to distribute the data belonging to a table evenly across all the data volumes of the data area.
Data Area
Size of the Data Area
The size of the data area must be at least 2,000 pages. There must also always be sufficient space in the data area to hold all the data that is created during database operations. You can configure your database in such a way that the database system automatically adds a new data volume as soon as the available storage space in the data area is too small.
More information:
Database Studio, Activating and Deactivating Automatic Extension of the Data Area
Database Manager CLI, auto_extend