To store data in a structured form, the database system uses the following access structures:
· Page chains for undo information and all C++ objects made persistent in liveCache database instances
· B* Trees for all other data
The database system automatically rebalances the B* trees, thereby making it unnecessary to reorganize the data manually.
If, in a transaction, a user changes data in the database, the database system first makes the data changes in the data cache and logs them in log entries (transaction logging).
At savepoints and whenever the data cache gets too full, the database system writes the data changes permanently in the data area (set of data volumes). The log entries are written to the log area (set of log volumes) by the log writer task.
In the converter, the database system stores the assignments of logical to physical data.
You can check the consistency of the B* trees and page chains; see Checking Database Structures.
See also:
Overview of the Database System